The random variable X is distributed normally with mean and variance 6, and the random variable Y is normally distributed with mean 8 and variance o. 2X-3Y is distributed normally with mean -12 and variance 42. Find

(a) the value of and the value of

a,

(b) P(X>8),

(c) P(Y <9),

(d) P(-4 <3X-2Y <7).