13.4. A process engineer is trying to improve the life of a cutting too]. He has run a 23 experiment using cutting speed (A). metal hardness (B), and cutting angle (C) as the factors. The data from two replicates are shown in Table 13E.2. (a) Do any of the three factors a'ect tool life? (b) What combination of factor levels produces the longest tool life? (c) Is there a combination of cutting speed and cut- ting angle that always gives good results regard- less of metal hardness? -I TABLE 13E.2 Data for the Experiment in Exercise 13.2 Replicate Run 1 II (1) 221 311 a .325 ' 435 'b '354 348 ab ,' "552 '3 '; 1 '472. c "440 453 be 605' 500 abc ' 392 ~ 419\