Consider a large ferry that can accommodate cars and buses. The toll for cars is $3, and the toll for buses is $10. Let x and y denote the number of cars and buses, respectively, carried on a single...

Consider a large ferry that can accommodate cars and buses. The toll for cars is $3, and the toll for buses is $10. Let
x
and
y
denote the number of cars and buses, respectively, carried on a single trip. Cars and buses are accommodated on different levels of the ferry, so the number of buses accommodated on any trip is independent of the number of cars on the trip. Suppose that
x
and
y
have the probability distributions shown below.