Two frequencies f1 and f2 are missing in the following table. If the mean of the distribution is 26 and the total number of observations is 40, find f1 and f2.
Class interval: 0–10 10–20 20–30 30–40 40–50
Frequency: 6 f1 10 f2 8
a) (6,10)
b) (7,9)
c) (8,8)
d) (5,11)