Answer
You have to divide the data into intervals. The minimum is 121 and the maximum is 169. Divide the data into 5 intervals:
121-130 customers occur 2 times.
131-140 occur 6 times.
141-150 occur 4 times
151-160 occur 3 times
161-170 occur 1 time.
Work Step by Step
Draw a bar to represent each interval's frequency: