-Suppose X follows normal distribution with mean 2. a) [6] If P(X < 4) = 0.8, find out P(0 < X < 2). b)[7] If X has variance 4, and P(X < a) = 0.3, what's a and P(X < a + 2)? c) [7] If X has variance 4, P(X > b) = 0.3, what's b and P(X > b + 2)? d) [2] What's the value of P(X = 2).

-Suppose the diameter at breast height (in.) of trees of a certain type is normally distributed with mean = 8.8 and = 2.8. a) [6] What's the probability that the diameter of a randomly selected tree will be between 5 and 10 in.? b) [6] What value c is such that the interval (8.8 c, 8.8 + c) includes 98% of all diameter values? c) [6] If 4 trees are independently selected, what's the probability that at least one has a diameter exceeding 10 in.?