In this X ~ N(100,10) and Y ~ N(90,5) in 000s For X, n=10 and for Y, n=5 X(bar) ~ N(100,1) and Y(bar) ~ N(90,5) But they have used value of X and Y in the solution P. S I don't know whether I am allowed to post photo of the question and the solution.
i think u didnt read the question clearly 10000 is standard deviation, hence in 1000s mean 10, 10^2 divided 10 is 10, and similary 5^2 didved by 5 is 5. so the solution is correct . check again and let me know. ' tanq!!