Demand in each period follows the same normal distribution (i.e., there is one demand distribution that represents demand in any single period). Assuming demand is independent across periods, which of the following statements about mean demand over five periods is true? 

a. It equals the mean of demand over one period. 

b. It is greater than the mean of demand over one period but less than five times the mean of demand over one period. 

c. It equals five times the mean of demand over one period. 

d. It is even more than five times the mean of demand over one period.