Shirley is a shelf stocker at the local grocery store. She has 4 varieties of Stouffer’s ® frozen...

Shirley is a shelf stocker at the local grocery store. She
has 4 varieties of Stouffer’s ® frozen dinners, 3 varieties of Lean Cuisine ®
frozen dinners, and 5 varieties of Weight Watchers ® frozen dinners. In how
many distinguishable ways can she stock the shelves if (a) the dinners can be
arranged in any order? (b) dinners from the same company are considered alike
and have to be shelved together? (c) dinners from the same company are
considered alike, but do not have to be shelved together?