The manager at a water park constructed the following frequency distribution to summarize attendance for 60 days in July and August.

Attendance ......Frequency

1,000 up to 1,250 ..... 5

1,250 up to 1,500 ..... 6

1,500 up to 1,750 .....10

1,750 up to 2,000 .....20

2,000 up to 2,250 .....15

2,250 up to 2,500 ..... 4

a. Calculate the mean attendance.

b. Calculate the variance and the standard deviation.