Use a tree to test whether the following argument is valid or invalid. if it is invalid, read off a counterexample. 1. (aab) v-( c d ) 2. a + (bvd) 3. -d+-(avb) : : a

Arestaurant offers delivery for their pizzas. the total cost the customer pays is the price of the pizzas, plus a delivery fee. one customer pays $23 to have 2 pizzas delivered. another customer pays $59 for 6 pizzas. how many pizzas are delivered to a customer who pays $86?