The numbers 1, 2, 3, and 4 are written on slips of paper, and 2 slips are drawn at random one at a time without replacement. Find the given probabilities. a. The sum of the numbers is 7. b. The sum of the number is 5 or less. c. The first number is 2 or the sum is 4. a. The probability that the sum of the numbers is 7 is (Type an integer or a simplified fraction.)