Pls help me solve homework

In a group of 50 first year students at Ryerson, 20 of them used the RAC in their time off, 25 of them used the student centre in their time off and 7 of them used neither service. If a student is randomly chosen from this group, calculate the following probabilities. Using a table might be helpful. A) The probability that a randomly chosen student uses both the RAC and the student centre. B) The probability that a randomly chosen student uses the RAC given that she uses the student centre. C) The probability that a student uses exactly one of the services. D) The probability that a student uses the RAC given that she uses exactly one of the services