If m(t)=f′(t)g′(t) for differentiable functions f and g with f′(t)=0, which of the following is the correct expression for dtdm?
a) [f′(t)]2f′(t)g′′(t)+g′(t)f′′(t)
b) [f′(t)]2g′(t)f′′(t)−f′(t)g′′(t)
c) [f′(t)]2f′(t)g′′(t)−g′(t)f′′(t)
d) f′(t)g′′(t)