Finding P-Values and critical values

Finding P-Values and critical values.  In exercise 17-24, assume that the significance level is a=0.05; use the given statement and find the P-value and critical values. 

18.  The test statistic of z = -2.00 is obtained when testing the claim that p <0.5.

20.  The test statistic of z = 1.50  is obtained when testing the claim that p ≠ 0.25.