Determine the sample size to survey customers of a store in a mall if there are 300 customers out of 5,000 in all of the corporation's stores. It presumes that the reliability level is 95 percent and the accepted margin of error is 0.05.

b. Determine the sample size of the previous year assuming that the sample of customers will be taken from one of the departments of the store where there are a total of 100 customers.