Let g be a differentiable function that is increasing and concave down on [1,5]. The integral I=∫15g(x)dx is approximated with four equal subintervals by the left sum L and by the trapezoidal sum T. Which of the following relationships among L,T, and I must be true?
a) T<L<I
b) L<I<T
c) L<T<I
d) T<I<L