20. Correct. The answer is false. dTC/dQ = MC = 4Q + 5. We employ three derivative rules to solve for dTC/dQ.

            a. Constant-Function Rule. The derivative of a constant function equals zero. Examples: If y = a, then dy/dx = 0. If f(Q) = 1,500; then df/dQ = 0.

            b. Power-Function Rule. If y = axn then dy/dx = naxn-1. Examples: If y = 0.5x4, then = dy/dx = 4*0.5x3. If y = x-3, the dy/dx = -3x-2

            c. Sum-Difference Rule. If y = f(x) + g(x), dy/dx = df/dx + dg/dx. Examples: d/dx(3x5 + 2x) = 15x4+ 2, d/dx (4x3 - 2x2 -5) = 12x2 - 4x, d/dx (ax2 - bx + c) = ax - b