A car producer claims a certain type of car is fuel-saving and can be driven 25 miles/gallon and a st dev of 2.8 miles/gallon.

An analyst wants to test this claim and wants a 1% risk of concluding the statement is false when it in fact is true. He chooses 30 observations.

Calculate the probability for type 2 error if the true mean is 24?

I tried:

X-bar critical = 26.32 and 23.68 and got P(-0.62 < Z < 4.53) = F(0.62)

But the book's answer is 0.64, how do I get there?