Intersection and conditional probability question

Suppose that a certain college class contains 42 students. Ofthese, 23 are juniors, 21 are social science majors, and 6 are neither. A student is selected at random from the class. (a) What is the probability: that the student is both a junior and a social science major? (b) Given that the student selected is a junior, what is the probability that he is also a social science major? Write your responses as fractions. (If necessary, consult a list of formulas.) (b)