A market research consultant hired by the Pepsi-Cola Co. is interested in determining who favors the Pepsi-Cola brand over Coke Classic in a particular urban location. A frame of customers from the market under investigation is provided in P8_44.XLS. 

a. Compute the proportion of the customers in the given frame who favor Pepsi. 

b. Use Excel to choose a simple random sample of size 30 from the given frame. 

c. Compute the proportion of the 30 customers in the random sample who favor Pepsi. Compare this sample proportion to the value obtained in part a. Explain any difference between the two values. 

d. What are the advantages and disadvantages of employing simple random sampling in this particular case?