HEL ASAP The keyboard life is normally distributed with a mean of 8 years with standard deviation
1.8 years.
The manufacturer will replace any such keyboard that wears out during the guarantee period.
The life of such keyboard is normally distributed.

a) If the guarantee period is 6 years, what percent of such keyboard will the manufacturer have to
replace?
b) How long should the guarantee run if the manufacturer wishes to replace no more
than 4.01% of keyboards?