A grouped frequency table with class intervals of equal sizes using 250 – 270 (270 not included in this interval) as one of the class intervals is constructed for the following data.
268, 220, 368, 258, 242, 310, 272, 342
310, 290, 300, 320, 319, 304, 402, 318
406, 292, 354, 278, 210, 240, 330, 316,
406, 215, 258, 236.
The frequency of class 310 - 330 is: