The first step to combat the Covid-19 is to develop an effective test kit. Suppose on average there are 1% chance being infected by the virus. One of the test being used will show negative for 99.5% of uninfected people. In addition, the test has only 0.4% of "false negative" rate.

(a) If you are tested positive, what is the chance that you are actually infected by the virus? What does your answer mean?

(b) If you are tested negative, what is the chance that you are actually infected by the virus? What does your answer mean?