Molly's Reach, a Regional Restaurant and Gift Shop, Has Recently

Molly's Reach, a regional restaurant and gift shop, has recently launched an increased sales campaign, particularly focused on their gift shop. To determine if their proposal is of interest, they plan to survey a random sample of their regular customers. Under consideration are several plans for selecting the sample. Name the sampling strategy for each.
a. Regular customers belong to a rewards program and have a customer rewards ID number. Randomly select 100 numbers.
b. Molly's Reach has stores in three different cities in northwestern U.S. and Canada. Randomly select one of the stores and survey all regular customers that belong to its rewards program.
c. Molly's Reach has an alphabetized list of regular customers who belong to their rewards program. After randomly selecting a customer on the list, every 25th customer from that point on is chosen to be in the sample.
d. Customers are grouped into four age categories (under 21, 21 to 35, 36 to 50, and over50). Randomly select 10 regular customers in each age category.