The systolic and diastolic blood pressure values (mm Hg) are the pressures when the heart muscle contracts and relaxes (denoted as $Y$ and $X,$ respectively). Over a collection of individuals, the distribution of diastolic pressure is normal with mean 73 and standard deviation $8 .$ The systolic pressure is conditionally normally distributed with mean $1.6 x$ when $X=x$ and standard deviation of $10 .$ Determine the following:
(a) Conditional probability density function $f_{Y \mid 73}(y)$ of $Y$ given $X=73$
(b) $P(Y<115 \mid X=73)$
(c) $E(Y \mid X=73)$
(d) Recognize the distribution $f_{X Y}(x, y)$ and identify the mean and variance of $Y$ and the correlation between $X$ and $Y$