This is a question from an assignment given in a Computational Algorithm class.

Ten research labs are attempting to determine the efficacy of proposed drugs in treating cancer. All the drugs are ordered from a pharmaceutical company (all ordered from the same one). Each of the labs want to order 1 drug to test. The choices are the following: Xenr, Phum, and Tsela.

The questions:

a.) How many orders are possible?

b.) Xenr appears promising. How many orders are there where at least 3 labs order Xenr?

c.) The pharmaceutical company announces it's running low on Tsela and only has enough for 2 labs. How many orders from the 10 labs can the company fill?

I am not sure which combinatoric principals would be used. a.) apppears it'd just be 10^3.