The Solubility of Silver Bromide Can Be Increased by Dissolving $\rightleftharpoons$

The solubility of silver bromide can be increased by dissolving it in a solution containing the thiosulfate anion.
AgBr(s) $\rightleftharpoons$ Ag⁺ (aq) + Br^- (aq) K₁ = 7.7 x 10^-13
Ag⁺(aq) + 2S₂O₃^2- (aq) $\rightleftharpoons$ Ag(S₂O₃) ₂^3- (aq) K₂ = 4.7 x 10¹³
What is the value of the equilibrium constant for the overall reaction
AgBr(s) + 2S₂O₃^2-(aq) $\rightleftharpoons$ Ag(S₂O₃) ₂^3-(aq) + Br^-(aq)

A) 3.6 x 10^-9
B) 12.4 x 10¹³
C) 4.7 x 10^-9
D) 4.7 x 10¹³
E) 36