Income (thousands of dollars) Number of families

0 - 20 15 20 - 50 75 50 - 100 60

Suppose you construct a percentage histogram with each horizontal unit representing one thousand dollars. Then the height of the rectangle over the first class interval (the one from 0 to 20) is equal to a. 0.5 b. 1.0 c. 1.5 d. 2.0 e. 2.5