Following distribution gives cumulative frequencies of 'more than type':
Marks Obtained | Number of students
≥ 5 30
≥ 10 23
≥ 15 8
≥ 20 2

Change the above data to a continuous grouped frequency distribution. Find the cummulative frequency corresponding to marks obtained in the range of 15 - 30.
A. 10
B. 8
C. 30
D. 23