In a study on reinforcement, a researcher allows a rat to choose between four arms of a plus maze. A plus maze is a maze shaped like a plus sign, with each extension from the center being called an "arm" in the maze. Upon being placed in the center of the maze, the probability on any given trial that a subject is reinforced in the left arm is .30, the right arm .30, the front arm .20, and the back arm .20.
(a) What is the probability the rat will be reinforced when entering the left or right arm?
(b) To make the optimal probability choice, a subject should enter the right or left arm on each trial. Explain why this is true.