Alex, Mel, and Chelsea play a game that has 6 rounds. In each round there is a single winner, and the outcomes of the rounds are independent. For each round the probability that Alex wins is \dfrac{1}{2}, and Mel is twice as likely to win as Chelsea. What is the probability that Alex wins three rounds, Mel wins two rounds, and Chelsea wins one round?
Answer Choices
A. \dfrac{5}{72}
B. \dfrac{5}{36}
C. \dfrac{1}{6}
D. \dfrac{1}{3}
E. 1