An industrial production process costs C(q) million dollars to produce q million units; these units then sell for R(q) million dollars. If C(2.1) = 5.1, R(2.1) = 6.9, MC(2.1) = 0.6, and MR(2.1) = 0.7, calculate
(a) The profit earned by producing 2.1 million units
(b) The approximate change in revenue if production increases from 2.1 to 2.14 million units.
(c) The approximate change in revenue if production decreases from 2.1 to 2.05 million units.
(d) The approximate change in profit in parts (b) and (c).