b) Taking a sample of size 4 and getting a sample mean of more than 26.

 

            n = 04

 ≥ 26

µ = 23.45

= 3.8

 

 

 

 

 

The probability of a z-value of 1.34 is: 0.5000 - 0.4099 = 0.0901 => 9.01%