Cystic Fibrosis Probability Questions?

As mentioned in class, cystic fibrosis is an inherited genetic disorder which can easily be detected by sequencing a person’s DNA coding for the CFTR protein. The DNA sequencing itself is very accurate. Suppose it is 99.5% accurate. However, the missing amino acid is not the only sequence that can cause the protein to malfunction. Suppose it accounts for about 80% of the cases of cystic fibrosis, while different sequences account for the remaining cases of cystic fibrosis. This was not known until more recently, as research into the disease developed. If we developed a test for cystic fibrosis, and we scored the test as positive only when the sequence matched that of people who were missing that amino acid (i.e. 80% of the time), then:
a.What is the sensitivity of the test? (80% or 99.5%)
b.What is the specificity of the test? (80% or 99.5%)
c.If cystic fibrosis affects 1 in 2000 Caucasians, and a Caucasian was tested at random for the disease, what would be the positive predictive value? Explain to a patient what this means in words someone who hadn’t had statistics could understand. (One sentence.)
d.What would be the negative predictive value? Explain to a patient what this means in words someone who hadn’t had statistics could understand. (One sentence.)
e.Without changing the sensitivity or specificity of this test, suggest a way could we improve its positive predict value. Be specific to the disease of cystic fibrosis.

I have no idea how to do this question..could someone show me how? Pleaseee !

I really appreciate it !