3. Let Let X1, X2, X3 be three random variables with normal distributions with mean, variances and covariances as following: . E[X]] = 4, E[X2] - 5, E[X3] - 6. . Var(X1) = 4, Var(X2) - 1, Var(X3) = 9, . Cov(X1, X2) = 1, Cov(X2, X3) - 2, Gov(X1, X3) - -3. Find P(X1 1 X2