The mean yield of wheat from a district A was 210 tones with S.D. 10 tones [er acre
from a sample of 100 plots. In another district B, the mean yield was 220 tones with
S.D. 12 tones from a sample of 150 plots. Assuming that the yield in the entire state
was 11 tones, test whether there is any significant difference between the mean yields
of crops in the two districts