The information below refers to the selling prices ($000) of homes sold in Warren, Pennsylvania, during 2016.

Selling Price ($000)                                 Frequency
120.0 up to 150.0 . . . . . . . . . . . . . . . . . . . .   4
150.0 up to 180.0 . . . . . . . . . . . . . . . . . . . . 18
180.0 up to 210.0 . . . . . . . . . . . . . . . . . . . . 30
210.0 up to 240.0 . . . . . . . . . . . . . . . . . . . . 20
240.0 up to 270.0 . . . . . . . . . . . . . . . . . . . . 17
270.0 up to 300.0 . . . . . . . . . . . . . . . . . . . . 10
300.0 up to 330.0 . . . . . . . . . . . . . . . . . . . .   6

a. What is the class interval?

b. How many homes were sold in 2016?

c. How many homes sold for less than $210,000?

d. What is the relative frequency of the 210 up to 240 class?

e. What is the midpoint of the 150 up to 180 class?

f. The selling prices range between what two amounts?