The Brinell scale is a measure of how hard a material is. An engineer hypothesizes that the mean Brinell score of all subcritically annealed ductile iron pieces is different from 170. The engineer measured the Brinell score of 25 pieces of this type of iron and calculated the sample mean to be 174 and the sample standard deviation to be 10. To test the engineer's claim, the critical value and test statistic are a. critical value: 1.6449 test statistic: -2 b. critical value:1.96 test statistic: -2 C. critical value:2.0639 test statistic 2 d. critical value: 1.7109 test statistic: 2