3) The length of time to complete a door assembly on a automobile factory assembly line is normally distributed with mean = 6.7 minutes and standard deviation = 2.2 minutes. For a door selected at random, what is the probability the assembly line will be

a) 5 minutes or less

**Solution: **Let_{}be the random length of time to complete a door assembly. The probability we are looking for is

_{}

b) 10 minutes or less

**Solution: **We need to find

_{}

c) between 5 and 10 minutes

**Solution: **Now we need to find

_{}

_{}

d) more then 10 minutes

**Solution: **Finally,

_{}