Let f be continuous, decreasing, and concave up on [2,8]. Using the same number n of equal-width subintervals, let L,R,M, and T denote the left-endpoint, right-endpoint, midpoint, and trapezoidal approximations, respectively, of ∫28f(x)dx. Which ordering from least to greatest must always hold?
a) L<T<M<R
b) R<M<T<L
c) M<R<T<L
d) R<T<M<L