The operator of a CNC machine gets paid $60/hour. It takes him 9 mini to load and unload a part (i. e. handling time), and 4 mini to change the cutting tool (which has Taylor coefficients of 0.251 and 900 m/min)|. When he runs the spindle at 900 rpm it finishes a part in 11 mini. His cutting tool costs him $95 each and he is able to machine 80 parts| before having to replace the tool. He wants to know if he can save money by running the spindle at 1400 rpm. What is the cost per part at 900 rpm and at 1400 rpm? C = vT^n rightarrow T_2/T_1 = (C/v_2)^1/n/(C/v_1)^1/n = (v_1/v_2)^1/n