a. X ~ N(66, 6.25)
b.[tex] z_{1} =\frac{65-66}{2.5}=-0.4[/tex]
[tex]z_{2} =\frac{69-66}{2.5}=1.2[/tex]
Using a standard normal probability table to find probability values for the z-scores, we get:
P(65 < X < 69) = 0.1554 + 0.3849 = 0.5403
c. z= 0.524 and -0.524
[tex]0.524=\frac{X-66}{2.5}[/tex]
1.31 = X - 66
X = 67.31
When z = -0.524, X = 64.69.
P(64.69 < X < 67.31) = 0.4