A couple goes to a restaurant for dinner. Below is a probability table in which X is the amount (dollars) on the meal spent by the husband and Y is the amount spent by the
wife.
X = 15
X = 20
X = 25
Y = 15
0.20
0.15
0.05
Y = 20
0.15
0.15
0.10
Y = 25
0.05
0.10
0.05
a. (7 pts) What is the probability that this couple spends 45 dollars or more?
b. (7 pts) Suppose that the restaurant is currently running a promotion with a
10% discount if the total amount spent by a table is 45 dollars or more.
What is expected total amount the couple actually has to pay?