Task 4 (10 marks) In machining process, surface quality of the machined parts is an important product quality factor. The measurement for surface quality is average surface roughness (Ra). Ra is mostly determined by the following cutting parameters: the cutting speed (V in m/min), the feed rate (f in mm/rev), and the depth of cut (a in mm). Tanikic and Marinkovic (2012) conducted a study that investigates the effects of these cutting parameters on average surface roughness (Ra). An experiment was carried out and the results obtained is as summarised in Table 2. Construct the least square regression equations for the output response in this experiment using each input factor (i.e. one least square regression equation for individual input factor against the output response) Compare the prediction of average surface roughness (Ra) using your least square regression equations against the multiple linear regression model obtained in Tanikic and Marinkovic (2012), that is: Ra = 3.1704 - 0.9442V + 0.6925f + 0.4856aTable 2. Experimental design and results (Tanikic and Marinkovic, 2012) Average surface Average surface Trial roughness, Trial roughness, no. V Ra no. V e Ra 1 80 0.071 0.5 3.6 15 110 0.196 2 3.33 2 80 0.071 1.25 3.61 16 110 0.321 0.5 3.73 80 0.071 2 3.96 17 110 0.321 1.25 4.005 80 0.196 0.5 4.3 18 110 0.321 2 4.23 5 80 0.196 1.25 4.955 19 140 0.071 0.5 1.13 6 80 0.196 2 5.92 20 140 0.071 1.25 2.79 7 80 0.321 0.5 5.13 21 140 0.071 2 3.08 80 0.321 1.25 5.28 22 140 0.196 0.5 1.85 9 80 0.321 2 5.98 23 140 0.196 1.25 2.835 10 110 0.071 0.5 2.32 24 140 0.196 2 3.27 11 110 0.071 1.25 2.745 25 140 0.321 0.5 3.52 12 110 0.071 2 3.44 26 140 0.321 1.25 3.605 13 110 0.196 0.5 2.55 27 140 0.321 2 3.66 14 110 0.196 1.25 3.405