Consider the definite integral ∫13x2dx. Using four equal subintervals, a student forms both the left-hand and right-hand Riemann sums, L4 and R4. Which of the following intervals is guaranteed to contain the exact value of the integral?
a) (6.75,8.75)
b) (8.75,10.75)
c) (6.75,10.75)
d) (7.75,9.25)