Let f(x)=x2, g(x)=x3, and h(x)=x, each differentiable at x=1. Which of the following correctly orders the instantaneous rates of change of the three functions at x=1 from greatest to least?
a) g′(1)>h′(1)>f′(1)
b) f′(1)>g′(1)>h′(1)
c) g′(1)>f′(1)>h′(1)
d) h′(1)>f′(1)>g′(1)