Two investments, $x$ and $Y,$ have the characteristics shown below.

$E(x)=$$$70$

$E(Y)=$$$100$

${}_x^2=7,000$

${}_Y^2=16,000,$

${}_{xY}=7,500$

If the weight of portfolio assets assigned to investment $x$ is $0\mathrm{.}4,$ compute the

a$.$ portfolio expected return and

b$.$ portfolio risk.