Subject: mathqa
Question: the mall charges 50 cents for the first hour of parking and $ 3 for each additional hour until the customer reaches 4 hours , after that the parking fee is $ 1 per hour . if a certain customer parked his in the mall for 7 hours and 30 minutes , how much is he going to pay ?
Option: 
A: $ 12 .
B: $ 13 .
C: $ 15 .
D: $ 11.5 .
Answer: B