Two persons $\mathrm{A}$ and $\mathrm{B}$, each roll a pair of dice, alternately till one of them gets a sum, equal to 4 or 7 and wins the game. If A starts the game the probability that he wins the game is
(a) $\frac{2}{7}$
(b) $\frac{4}{7}$
(c) $\frac{3}{7}$
(d) $\frac{5}{7}$