=+12. Newly purchased automobile tires of a certain type are supposed to be filled to a pressure of 34 psi. Let 

denote the true average pressure. A test of H0:  5 34 versus Ha:  Þ 34 will be based on a large sample of tires so that the test statistic z 5 (x 2 34)y(s1n) will have approximately a standard normal distribution when H0 is true. Determine the value of z and the P-value in each of the following cases:

a. n 5 50, x 5 34.43, s 5 1.06

b. n 5 50, x 5 33.57, s 5 1.06

c. n 5 32, x 5 33.25, s 5 1.89

d. n 5 36, x 5 34.66, s 5 2.53