A real estate sales agency records indicate that the mean selling time of house property is 100 days. Because of pandemic conditions, the agency believes that the mean selling time is now greater than 100 days. A survey of 136 recently sold houses revealed a mean selling time of 130 days, with a standard deviation of 30 days.

a)State your null and alternative hypothesis.

b)At the .10 significance level, has there been an increase in selling time?

c)What is your conclusion?