Shannon went to an auto repair shop and paid $339.50, which included parts that cost $112 and 3.5 hours of labor. Joni went to an auto repair shop and paid $455, which included parts that cost $310 and 2.5 hours of labor. Which correctly compares the cost of the labor?
A Shannon paid $7 more per hour for labor.
B Shannon paid $7 less per hour for labor.
C Joni paid $85 more per hour for labor.
D Joni paid $85 less per hour for labor.