Customers Arrive at the Local Grocery Store at a Steady

Multiple Choice

Customers arrive at the local grocery store at a steady rate of 40 an hour. Thirty percent of these customers purchase 10 items or less and go to the express line where they enjoy an average checkout time of 5 minutes. Customers that don't meet the express line criterion go to the other checkout line where they spend an average of 10 minutes checking out. How many people are checking out in the express line on average?

A) 1.0
B) 3.0
C) 12
D) 144