Probability of developing a lung cancer disease

I need to solve this problem:

A cohort study is done to assess the impact of smoking on lung cancer. In this study, a large representative sample of first year university students are followed for 40 years. For each student, the smoking status is recorded as well as the lung cancer status at the end of the follow-up period. In the cohort, 20% of students smoked and among those, 50% developed lung cancer. Among the remaining students, 6.25% developed lung cancer.
a) Compute the probability of developing a lung cancer.
b) Is developing lung cancer independent of smoking? Why?
c) Using Bayes' rule, compute the conditional probability of smoking given the development of a lung cancer.

I have no idea where to start... Could anybody help me?
It is for Introduction to Statistical Modelling I. Could you please just set up the contingency table for me... My teacher never talked about that in class