The data below shows the daily electricity consumption (in kilowatt hours) for 50 randomly selected household. Use 15 as the lower class limit of the first class to construct a histogram for daily electricity consumption with 6 classes.

16	18	20	23	23	24	24	25	25	25
26	26	26	26	26	27	27	28	28	28
28	29	29	30	30	30	31	31	31	32
32	32	32	33	33	33	33	33	34	34
34	35	35	35	36	37	38	39	42	46

With xas the upper class limit of the second class, what is the relative frequency of class (21 to x)?