A sample of an arsenic compound weighing 0.3245 g was dissolved and all the arsenic converted to arsenic in the +3 oxidation state. A 0.0250 M solution of a reagent, R, was added which oxidized the arsenic to the +5 oxidation state. R contains a metal in the +4 state that was reduced to the +2 state. If it took 15.64 mL of the solution of R to exactly react with the arsenic, what is the percentage of arsenic in the sample?
a) 1.107 b) 1.694 c) 18.05 d) 22.57 e) 9.027