The cost of manufacturing x cases of cereal is C dollars, where C = 3x + 4√x + 2. Weekly production at t weeks from the present is estimated to be x = 6200 + 100t cases. (a) Find the marginal cost, dC/dx. (b) Find the time rate of change of cost, dC/dt. (c) How fast (with respect to time) are costs rising when t = 2?