Answer
11.51% of customers will receive service for half price.
Work Step by Step
$\mu$ = 17, $\sigma$ = 2.5
Want to find $P( x > 20 )$
i) Convert 20 to a z-score:
z = $\frac{x - \mu}{\sigma}$
z = $\frac{20 - 17}{2.5}$
z= 1.2
ii) $P(x > 20)
= P(z > 1.2)
= 1 - P( z < 1.2)
= 1-0.8849
= 0.1151
11.51% of customers will receive service for half price.
