calculation of cutting speed for minimum total cost

Question

For a certain job, the cost of metal cutting is Rs.18C/V and the cost of tooling is Rs.270 C/(TV). Where C is a constant, V is the cutting speed in m/min and T is the tool life in minutes. The Taylor’s tool life equation is VT^0.25 = 150. The cutting speed (in m/min) for the minimum total cost is ____