Defendant contends first that this action as a matter of law is barred by the three years statute of limitations' which statute she properly pleaded. We disagree.
 An agreement to sell or purchase real property is governed by the general law of contracts. 7 Strong, N. C. Index 2d, Vendor and Purchaser, § 1, p. 489. “Where an option or contract to purchase does not specify the time within which the right to buy may be exercised, the right must be exercised within a reasonable time.” Ibid, § 2, p. 492.
*519In Lewis v. Allred, 249 N.C. 486, 106 S.E. 2d 689 (1959), Denny, J. (later C.J.) quoting from 49 Am. Jur., Statute of Frauds, § 356, p. 667 said:
“ ‘A memorandum of an agreement for the sale of land is not necessarily insufficient to satisfy the requirements of the statute of frauds because the time for performance is not stated therein. In case of an executory contract of sale, where the time for the execution of the conveyance or transfer is not limited, the law implies that it is to be done within a reasonable time, and the failure to incorporate in the memorandum such a statement does not render it insufficient. * * * ’ ”
 Ordinarily, the bar of the statute of limitations is a mixed question of law and fact. But where the law is properly pleaded and all the facts with reference thereto are admitted the question of limitations becomes a matter of law. Poultry Co. v. Oil Co., 272 N.C. 16, 157 S.E. 2d 693 (1967); Mobley v. Broome, 248 N.C. 54, 102 S.E. 2d 407 (1958).
In Etheridge v. R. R., 209 N.C. 326, 183 S.E. 539 (1936), we find:
While it is a maxim of English law that “how long a ‘reasonable time’ ought to be is not defined in law, but is left with the discretion of the judge” (Coke Litt. 50), this applies only where the facts are admitted, or clearly proved, and “Where the question of reasonable time is a debatable one, it must be referred to the jury for decision.” Hoke, J., in Holden v. Royall, 169 N.C., 676 (678), said: “And, in this State, authority is to the effect that, where this question of reasonable time is a debatable one, it must be referred to the jury for decision. (Citations.)
In Trust Co. v. Insurance Co., 199 N.C. 465, 154 S.E. 743 (1930), we find:
“ * * * If no time for the performance of an obligation is agreed upon by the parties, then the law prescribes that the act must be performed within a reasonable time. Reasonable time is generally conceived to be a mixed question of law and fact. ‘If, from the admitted facts, the court can draw the conclusion as to whether the time is reasonable or unreasonable by applying to them a legal principle or a rule of law, then the question is one of law. But if differ*520ent inferences may be drawn, or the circumstances are numerous and complicated, and such that a definite legal rule cannot be applied to them, then the matter should be submitted to the jury. It is only when the facts are undisputed and different inferences cannot be reasonably drawn from them, that the question ever becomes one of law.’ (Citations.) ”
In Claus v. Lee, 140 N.C. 552, 53 S.E. 433 (1906), the court said:
“ * * *The result of our examination leads us to the conclusion that what is ‘reasonable time’ is generally a mixed question of law and fact, not only where the evidence is conflicting, but even in some cases where the facts are not disputed; and the matter should be decided by the jury upon proper instructions on the particular circumstances of each case. (Citations.)”
 While supporting the principle that determination of “reasonable time” is generally a mixed question of law and fact and thus for the jury, there are cases which hold that when facts are simple and admitted and only one inference can be drawn, the determination of “reasonable time” is a question of law. See Colt v. Kimball, 190 N.C. 169, 129 S.E. 406 (1925); Huff v. R. R., 171 N.C. 203, 88 S.E. 344 (1916); and Holden v. Royall, 169 N.C. 676, 86 S.E. 583 (1915).
 Applying the quoted principles to the case at bar, it is obvious that all the facts with respect to the statute of limitations were not admitted and that more than one inference could be drawn from the evidence. In this case we think the question of “reasonable time” is a debatable one and was properly submitted to the jury upon instructions to which there was no exception.
 Defendant contends that the trial court erred in not sustaining her plea of res judicata. We reject this contention.
In Shaw v. Eaves, 262 N.C. 656, 661, 138 S.E. 2d 520 (1964), in an opinion by Clifton L. Moore, J., we find:
“ * * * In order for a judgment to constitute res judi-cata in a subsequent action there must be identity of parties, subject matter, issues and relief demanded, and it is required further that the estoppel be mutual. Light Co. v. *521 Insurance Co., 238 N.C. 679, 79 S.E. 2d 167; Stansel v. McIntyre, 237 N.C. 148, 74 S.E. 2d 345; Cameron v. Cameron, 235 N.C. 82, 68 S.E. 2d 796; Leary v. Land Bank, 215 N.C. 501, 2 S.E. 2d 570. In order for a party to be barred by the doctrine of res judicata, it is necessary not only that he should have had an opportunity for a hearing but also that the identical question must have been considered and determined adversely to him. Crosland-Cullen Co. v. Crosland, 249 N.C. 167, 105 S.E. 2d 655. * * * ”
Relating the instant case to the former action, while there might have been identity of parties and subject matter, the issues and relief demanded in the two actions are different and the principal questions presented by the present action were not considered and determined adversely to plaintiffs in the former action. The former action presented the question as to whether W. T. Yancey was the owner of one-third interest in the subject property; the present action submits the questions whether there was a valid and subsisting contract between Watkins and Yancey with reference to one-third interest in the land and, if so, is Yancey entitled to enforce the contract and what amount is Yancey entitled to recover for breach of the contract.
We have carefully considered the other questions presented in defendant’s brief but find them to be without merit. We hold that this action was properly submitted to the jury on appropriate issues and that the trial was free from prejudicial error.
Judges Campbell and Graham concur.