Assume that C(x) is in dollars and x is the number of units produced and sold. For the total-cost function C(x) = 0.01x² + 0.6x + 40, find ΔC and C'(x) when x = 70 and Δx = 1.
a) ΔC = $0.61, C'(x) = 1.3
b) ΔC = $0.71, C'(x) = 1.4
c) ΔC = $0.81, C'(x) = 1.5
d) ΔC = $0.91, C'(x) = 1.6