how do i work out question 9

Boxes A and B contain 4 counters each. Box A contains two red and two yellow counters and box B contains three red and one yellow counters. A box is chosen at random and then a single counter is selected. What is the probability of selecting box B and a red counter? T IB / E/ E T TREE TE A B C 4 RRT TRE RE N | - 00 | - D E /ET ER E ET ER EE