P appoints A, a minor, 17 years of age, his agent to sell his car. A sells the car to X. Soon thereafter, the price of cars went up with the floating rate of the peso and P promptly sought to disaffirm the sale and brought an action to recover the car on the ground that A's act was void since a minor cannot be agent. May P avoid the contract entered into by A in favor of X on the ground of his agent's incapacity