What type of experimental design would you recommend in each of the following cases? Suggest in some detail how you would design each study:

a. A test of three methods of compensation of factory workers. The methods are hourly wage, incentive pay, and weekly salary. The department variable is direct labor cost per unit of output.
b. A study of the effects of various levels of advertising effort and price reduction on the sale of specific branded grocery products by a retail grocery chain.
c. A study to determine whether it is true that the use of fast-paced music played over a store's public address system will speed the shopping rate of customers without an adverse effect on the amount spent per customer.