Question 1176406
z+(x-mean)/sd
a. z < (20-24)/7 or z < -4/7 probability  is 0.2839
b.  z between 0 and 8/7. That probability is 0.3735
can do on calculator with 2nd VARS2 normalcdf (24,32,24,7)
c. more than 40 minutes, can do the same way picking a high top end like 100
probability is 0.0111
it is also the probability z > 16/7