here is my question

5. 1 Let X and Y be normal random variables with unknown means and known variances. We take random samples of X and Y, X1, ..., Xnx, Yl, ..., Yny. We test the hypotheses Ho : MX = MY, H1 : MX # MY using a test which has critical region C = {(x1, . .., nx , yl, . .., yny) : 0$ 1 }, where I is the two-sided 90% confidence interval for the difference ux - my determined by the data (21, . . ., Inx , yl, . . ., yny ). Compute the significance level of this test