Another pizza parlor is having a super special. They have a rack of small pizzas, each with three or four different toppings. The price is really low because they forgot to indicate on the boxes what toppings were on each pizza. They had eight toppings available, and they made one pizza for each of the possible combinations of three or four toppings.

1. How many pizzas are on the rack?

2. What is the probability of getting a pizza that has mushrooms on it?

   Hint (b):

   If mushrooms are a known topping, then you choose one fewer topping from only 7 remaining toppings.

   Answer (b):

   $\frac{_{7}C_{3}+_{7}C_{2}}{126}=\frac{56}{126}=\frac{4}{9}$