[Exer12-2] Exercise 55 of Book {Devore2017B} P.177
Suppose the time (in hours) taken by a homeowner to mow his lawn(修剪他的草坪) in an rv $X$ having a gamma distribution with parameters $\alpha=2$ and $\beta=\frac{1}{2}$. What is the probability that it takes:
- (a) At most $1$ hour to mow the lawn?
- (b) At least $2$ hours to mow the lawn?
- (c) Between $.5$ and $1.5$ hours to mow the lawn?