Answer:
Hence, the probability is:

Explanation:
Each of four friends orders a sweatshirt from a catalog.
There are 15 colors of sweatshirts, 5 of which are all cotton and 10 of which are a blend.
We have to find the probability that the friend order only cotton sweatshirt:
As there are 5 cotton shirts out of which four are to be selected from a total of 15 coloured shirts.
Now we know that a probability is defined as:
Probability=( Number of favourable outcomes)/(Total number of outcomes)/( Total number of outcomes)
So, the probability is:

Hence, the probability is:
