In the Reddy Mikks model of Example 2.2-1:

(a) Determine the range for the ratio of the unit revenue of exterior paint to the unit revenue of interior paint.

(b) If the revenue per ton of exterior paint remains constant at $6000 per ton, determine the maximum unit revenue of interior paint that will keep the present optimum solution unchanged.

(c) If for marketing reasons the unit revenue of interior paint must be reduced to $2500, will the current optimum production mix change?