(a(i))[2]
The variable $X$ hours, representing the amount of sleep people get in one night, follows a normal distribution with mean $7.15$ hours and standard deviation $0.88$ hours. Find the probability that a person selected at random sleeps for under $8$ hours in one night.
(a(ii))[3]
Determine the value of $q$ for which $P(X < q) = 0.75$.
(b)[3]
The random variable $Y$ is distributed as $N(\mu, \sigma^2)$, with $2\sigma = 3\mu$ and $\mu \neq 0$. Find $P(Y > 4\mu)$.