Question 836254
a)

Z*_Upper = (76 - 62.7)/2.5 = 5.32
Z*_Lower = (57 - 62.7)/2.5 = -2.28


The requirement is to get p(-2.28 < Z < 5.32) = p(Z<5.32) - p(Z<-2.28).

Use normal distribution table to get the answer for p and multiply with 100 to get the percentage.

For the rest, after this hint if you are still struggling to solve then contact me.

Cheers!