At a school's open house, T-shirts and sweatshirts were sold. Each item was purchased by either a student or a parent. The two-way frequency table summarizes a random sample of 50 items sold that night. T-shirt 12 Sweatshirt 11 Student Parent 18 9 Let student be the event that an item randomly chosen from among those sold was purchased by a student. Let T-shirt be the event that an item randomly chosen from among those sold was a T-shirt. Find the following probabilities. Write your answers as decimals. (If necessary, consult a list of formulas.) (a) P(T-shirt) (b) P(student and T-shirt) - O (c) P(student | T-shirt) - O X 5