The Energy of a System Increases at a Rate of 3.5

Multiple Choice

The energy of a system increases at a rate of 3.5 t + 6.2 t², in joules.What is the instantaneous power at t = 3.1 s?

A) 3.5 W
B) 6.2 W
C) 16 W
D) 42 W
E) 70 W