I'm not understanding this and what I am doing wrong. Can you help show me in steps so I can see where I am getting messed up? Thanks!

Below is the problem I am working on and need help with:

Since both population standard deviations are known, the ztest is used. The null hypothesis H0 is that the population mean voltage for batteries produced by manufacturer A is the same as those produced by manufacturer B. The alternative hypothesis Ha is that the population mean voltage is different for batteries produced by each manufacturer. Since the claim is that the two population means differ, the hypothesis test is twotailed. . . . . 51 52 The test statistic 2: is calculated using the formula 2 = 0% 03:; Ti E Since the number of samples from each manufacturer is the same, 711 : n2 2 89. E E 127 126 % = m 2.98. '71 '72 32 12 a t n: a a Performing a twotailed ztest with z 2 2.98 yields a pvalue of P(z :1 2.98 or z 2 2.98) a 0.002. Since the pvalue is less than the signicance level (0.002