A postal service is considering using a new system to read postcodes. To check how accurately the new system reads postcodes, the same letters are placed through the machine several times. The table below summarizes the number of errors.

Class	Frequency
(0, 12]	8
(12, 24]	3
(24, 36]	12
(36, 48]	4
(48, 60]	5
(60, 72]	3

What is the cumulative frequency for the (36, 48] class?