4.) according to the local la union president, the mean income of plumbers is normally distributed with a mean of $60,000 and a population standard deviation of $6,000.An investigative reporter for the local television station took a sample to try to disprove that claim. The sample size consisted of 20 plumbers with a mean income of $62,500. At the 5% level of significance, is it reasonable to conclude that the mean income is different than $60,000? a) state the null and alternative hypotheses b) is this a one-tailed or two-tailed hypothesis text? c) find the critical value d) calculate the test statistic e) calculate the p-value f) what is your decision about the null hypothesis