Answer:
0.09
Step-by-step explanation:
Let x = ages of mother
x  :  22  17   27   20   23   19    24   18   19   24
N = 10
Mean = ∑x/N = 218/10 = 21.8
Difference in mean = 21.8 - 20 = 1.8
If significance level = 5% or 0.05
∴ Rejection region = 1.8 X 0.05 = 0.09