height of students is normally distributed

Mean = 67

standard deviation = 4

what portion of students that are over 67 inches tall are also under 70 inches tall?

I get a z value of .5 for 67 inches and .9332 for 70 inches

If I simply divide the z value of .9332 by .5 I get 1.8664, which is obviously wrong because it is more than 1.

Would the correct answer be:

(.9332 - .5000) / .5000

= 8664?