The marks of 30 students of a class, obtained in a test (out of 75), are given below :
42, 21, 50, 37, 42, 37, 38, 42, 49, 52, 38, 53, 57, 47, 29, 59, 61, 33, 17, 17, 39, 44, 42, 39, 14, 7, 27, 19, 54, 51.
Form a frequency table with equal class intervals.