Mikasa is a branch manager and decided to work on the time that any customer wait to get their work done at banks. Mikasa collected the following results: 9, 11, 3, 6, 8, 20, 12, 25, 4, 6, 7, 4, 10, 12, 14, 16, 21, 21, 25, 30, 22, 10, 7, 8, 5.

a) Construct a frequency table (include cumulative frequency) for Mikasa's data.

b) Construct a histogram graph, frequency polygon graph, and cumulative-frequency diagram (plot on the same grid).