$I_2 + I^- \rightleftharpoons I^-_3$ This reaction is set-up in aqueous medium. Initially we have 1 mole of $I_2$ and 0.5 mole of $I^-$ in 1 L flask. After equilibrium is reached, excess of $AgNO_3$ gave 0.25 mole of yellow ppt. Equilibrium constant is

Question

(a) 1.33

(b) 2.66

(c) 2.00

(d) 3.00