The marginal cost and revenue of a small business, in thousands of dollars per day, t days after its grand opening is given by C'(t) = 11t + 40 and R'(t) = t2 + 50 respectively. For 0 < t < 9, which of the following is true? O The profit is minimal at t = 5.5 O The profit is minimal at t = 1 O The profit is maximal at t = 0.5 O The profit is maximal at t = 5.5 O The profit is maximal at t = 1 O The profit is minimal at t = 0.5