The quantity of charge q (in coulombs) that has passed through a surface of area 2.05cm2 varies with time according to the equation q=7t3−6t+6, where t is in seconds. What is the rate of change of charge with respect to time at t=2 seconds?
a) 30 C/s
b) 44 C/s
c) 56 C/s
d) 68 C/s