Question 1119809
a. No cell phone for each of 9 is 0.76^9=0.0846
b. This would be 9C3*0.24^6*0.76^3=0.0070.  The expected value would be 2.16 (.24*9), so this is a reasonable probability.
c. The expected value above of 2.14 is np, and that is the mean value of houses.