Hi,
Using Excel function NORMSDIST
P(X <2.5)= P( z = (2.5-4.8)/0.89) = P(z = -2.584)) = NORMSDIST(-2.5841) = .00493
Let You finish these up ...
P(3 ≤ x ≤ 4) = P(x< 4) - P(x<3)= P( z = (4-4.8)/0.89) - P( z = (3-4.8)/0.89)
P(X > 4.2) = 1 - P(x < 4.2)) = 1 - P( z = (4.2-4.8)/0.89 ) =
1 - NORMSDIST(-.8989) = 1 - .184 = .816 Or 81.6%