An envelope contains eight bills: 2 ones, 2 fives, 2 tens, and 2 twenties. Two bills are drawn at random without replacement. What is the probability that their sum is \$ 20 or more?
Answer Choices
A. \dfrac{1}{4}
B. \dfrac{2}{5}
C. \dfrac{3}{7}
D. \dfrac{1}{2}
E. \dfrac{2}{3}