Consider the follow theorem: If x is a positive integer less than 4, then (x1)3 24X. Which set of facts must be proven in a proof by exhaustion of the theorem? a. 23 2 41 23 2 42 43 243 O b. 23 2 41 23 2 42 43 243 532 44 C. 332 42 43 2 43 Od. ,3 340 23 2 41 23 2 42 43 243