Marginal cost =dxddC​ ​=dxd​(0.007x3−0.003x2+15x+4000)=0.021x2−0.006x+15​ Now, when x=172=MC is​=0.021(17)2−0.006×17+15=6.069−0.102+15=20.967​ Therefore, required Marginal cost is Rs. 20.97.