Refer to the Following Ages (Rounded to the Nearest Whole

Multiple Choice

Refer to the following ages (rounded to the nearest whole year) of employees at a large company that were grouped into a distribution with class limits:
20 up to 30
30 up to 40
40 up to 50
50 up to 60
60 up to 70
What is the class interval and the midpoint of the first class?

A) 20 and 25
B) 20 and 24.5
C) 10 and 25
D) 10 and 24.5
E) None of the choices are correct