Bob wants to run a mile in the same time as his sister. If Bob’s time for a mile is currently 10 minutes 20 seconds and his sister’s time is currently 9 minutes 36 seconds, by what percent does Bob need to improve his time in order run a mile in the same time as his sister? Choose the correct option
A) 3 %  B) 5 %  C) 7 %  D) 10 %  E) 12 %

Rationale: "bob ' s time = 620 secs . his sis ' time = 576 secs . percent increase needed = ( 620 - 576 / 620 ) * 100 = 44 / 640 * 100 = 7 % . ans ( c ) ."
Answer: C