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## Homework Statement

in how many different ways can 7 different books be arranged in a row if

a. 3 specified books must be together,

b. two specified boks mus occupy both ends

## Homework Equations

i dont udnerstand wether it is a permutation or a combination.

## The Attempt at a Solution

a. 4! x 7!

b. 7 x 5! x 6