Consider f(x)=ex on the interval [0,1]. A midpoint Riemann sum with two equal-width subintervals is used to approximate ∫01exdx. Which statement about the approximation is correct?
a) It overestimates the integral because f is increasing on [0,1].
b) It overestimates the integral because f is concave up on [0,1].
c) It underestimates the integral because f is concave up on [0,1].
d) It gives the exact value of the integral because the midpoint rule is exact for ex on [0,1].