Question 1171108
the mean is np=75*0.20=15
the variance is np(1-p)=15*0.8=12
the sd is sqrt(V)=3.464
10% is 7.5 customers (we would consider 8 the bottom number)
40% is 30 customers
with the continuity correction factor, we would use 7.5  and 30.5 for the two values.
z=(7.5-15)/3.464 with z of -2.165
for 30.5
z=(30.5-15)/3.464
=+4.47
the probability of z's being in between those values is 98.5%