Tony likes playing football and computer games. Playing football for 30 minutes and Minecraft for 20 minutes makes him as satisfied as playing football for 10 minutes and Minecraft for 50 minutes. Suppose that he plays Minecraft for 35 minutes now, and his preferences are convex.

Given only this information about Tony's preferences, what is the theoretical maximum time he could spend playing football to be as well off as in the previous two situations? Please insert a numerical value only.