The pet store sells a lot of pet food. On a slow day at the pet store, three people buy cat food, two people buy dog food, and one person buys food for a pet snake. If half of the customers pay in cash and half-pay with a credit card, what is the probability that a customer buying pet food will buy dog food with cash? Set up an area model like Edwin's in part c of problems 5-77 to help you find the probability.