The following are heat producing of coal capacities fro two
mines( in millions of calories per tonne)
Mine A: 8500, 8330, 8480, 7960, 8030
Mine B: 7710, 7890, 7920, 8270, 7860
Assume that the data constitute independent random samples from
normal distributions with equal variances. Test at the 0.01 level
of significance whether the means of the heat-producing capacities
of coal from two mines is different.