13-P7. A man attempts to support a stack of books horizontally by applying a compressive force of F = 120 N to the ends of the stack with his hands.

If each book has a mass of 0.95 kg,determine the greatest number of books that can be supported in the stack. The coefficient of static friction between his hands and a book is (u)h = 0.6 and between any two books (u)b = 0.4.