A mechanical engineer is investigating the surface nish of metal parts produced on a lathe and its relationship to the speed ofthe lathe. Twelve testing have been conducted by varying the lathe's speed for each testing and surface finish have been measured by using profilometer. Table 1.1 shows the lathe speed (in RPM} and surface nish for each testing. Table 1.1 Sutface nish dale. Lathe speed 224 204 241 245 235 24? 265 259 221 218 224 212 (inRPM) (c) Find the least square regression line, 3.} : a. + bat for lathe speed and surface nish. Interpret the value of a and b