Stat help please

Engineers want to design seats in commercial aircraft so that they are wide enough to fit 90% of all males. (Accommodating 100% of males would require very wide seats that would be much too expensive.) Men have hip breadths that are normally distributed with a mean of 14.2 in. and a standard deviation of 1.2 in. Find P90. That is, find the hip breadth for men that separates the smallest 90% from the largest 10%.