Answer
a) $0.1587$
b) $\frac{1}{2}$
Work Step by Step
a)
$p(X\geq45)$ = $1-p(X\leq45)$ = $1-F(\frac{45-40}{5})$ = $1-F(1)$ $\approx$ $1-0.8413$ $\approx$ $0.1587$
b)
$p(0\leq{X}\leq40)$ = $p(X\leq40)$ - $p(X\leq0)$ = $F(\frac{40-40}{5})-F(\frac{0-40}{5})$ = $F(0)-F(-8)$ $\frac{1}{2}-F(-8)$ $\approx$ $\frac{1}{2}-0$ = $\frac{1}{2}$
