Hello, iMoons!

Here's the first part . . .

There are: . possible orders for the 15 phones.Fifteen telephones has just received at a service center.

Five are cellular , five are cordless , and five conventional corded phones .

(a) If phones are randomly selected for service, what is the probability

. . .that all the cordless phones are serviced first?

There isway for the -phones to be first.one

The other 10 phones can follow in: . ways.

Hence, there are: . ways for the -phones to be first.

Therefore: .

I'm still working on the second part . . .

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