(i) Taking class intervals as 0.00, −0.04, 0.04, −0.08, and so on, a grouped frequency table can be constructed as follows.

The number of days for which the concentration of SO2 is more than 0.11 is the number of days for which the concentration is in between 0.12 − 0.16, 0.16 − 0.20, 0.20 − 0.24.

(ii) Required number of days = 2 + 4 + 2 = 8 Therefore, for 8 days, the concentration of SO2 is more than 0.11 ppm.