Hello, ibetan!

A television director is scheduling a certain sponsor's commercials

for an upcoming broadcast. There are six slots available for commercials.

In how many ways may the director schedule the commercials?

a) If the sponsor has 6 different commercials, each to be shown 1 time?

(This one I know is 6!) . Good!

Call the commercials: .b) If the sponsor has 3 different commercials, each to be shown 2 times?

Then there are: . ways.

Call the commercials: .c) If the sponsor has 2 different commercials, each to be shown 3 times?

Then there are: . ways.

Call the commericals: .d) If the sponsor has 3 different commercials, the first is to be shown 3 times,

the second 2 times and the third 1 time?

Then there are: . ways.