3. (6 points) Let X1, X2, ..., Xs be a random sample of SAT mathematics scores, assumed to be N(ux, 02), and let Y1, Y2, ..., Ys be and independent random sample of SAT verval scores, assumed to be N(uy, 0?). If the following data are observed, find a 90% confidence interval for ux - HY: X1 = 644, X2 = 493, X3 = 532, X4 = 462, Xs = 565. Y1 = 623, Y2 - 472, Ya - 492, Y4 = 661, Ys = 540, Yo = 502, Yr = 549, Ys = 518