Solve Write Your Answer in Simplest Form $3 \frac { 2 } { 5 }$

Multiple Choice

Solve. Write your answer in simplest form.
-Brian was training to run a marathon. During the three-day period before the race he decided that he would train for a total of 12 hours. If he trained for $3 \frac { 2 } { 5 }$ hours on the first day and $3 \frac { 7 } { 10 }$ hours on the second day, how many hours would he need to train on the third day?

A) $4 \frac { 9 } { 10 }$ hours

B) $5 \frac { 1 } { 10 }$ hours

C) 5 hours

D) $5 \frac { 9 } { 10 }$ hours