The Normal Distribution · Challenge problem

Exam scores are normal. The top $10\%$ earn an A, which requires at least $88$ points, and the bottom $10\%$ fail, which means scoring below $56$. Using $\Phi(1.28) = 0.90$ and $\Phi(0.64) = 0.7389$, what fraction of students score between $64$ and $80$? Give four decimal places.