For Standard 9/1

I am here to correct my latest quiz, the Hardy Weinberg equilibrium quiz.

After Graduation, you and 19 friends build a raft, sail to a deserted island, and start a new population, totally isolated from the world. Two of your friends carry (that is, are heterozygous for) the recessive cf allele, which in homozygotes causes cystic fibrosis, Assuming that the frequency of this allele does not change as the population grows, what will be the instance of cystic fibrosis on your island?

Well at the time that I took this quiz, I was not too confident with my knowledge of the gene pool. 
So in this problem 2/20 people are heterozygous, which means that 2 out of the 40 alleles total that this group of people has, are recessive. In this problem, we are asked to find the instance of cystic fibrosis, or otherwise known as q^2.

So 2/40 is q.
So to find what q^2 is, we simple square 2/40.
so (0.05)^2 is equal to

0.0025.

When I first took this quiz, I was having trouble understanding this because my mind was aware of the fact that if a population has all homozygous dominant, except for two heterozygous, that you were able to say that 2 out of  these 40 alleles (2 per person) are recessive. As I was walking out of the Biology Classroom, this clicked in my head, but too late for it to make a difference in my quiz.