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?  Choose one:
A) $ 11.5 .
B) $ 12 .
C) $ 13 .
D) $ 14.5
E) $ 15 .

Rationale: charges for 7 hours = ( first hour @ $ 0.50 ) + ( 3 hours @ $ 3 ) + ( 3.5 hours @ $ 1 ) charges for 7 hours = ( 1 @ $ 0.50 ) + ( 3 hours @ $ 3 ) + ( 3.5 hours @ $ 1 ) charges for 7 hours = ( $ 0.50 ) + ( $ 9 ) + ( $ 3.5 ) charges for 7 hours = ( $ 0.50 ) + ( $ 9 ) + ( $ 3.50 ) charges for 7 hours = $ 13 hence correct answer must be ( c )
Answer: C