Arsenic Acid, H₃AsO₄, Is Used Industrially to Manufacture Insecticides

Arsenic acid, H₃AsO₄, is used industrially to manufacture insecticides. Arsenic acid is a polyprotic acid with K₁ = 2.5 * 10¯⁴, K₂ = 5.6 * 10¯⁸, and K₃ = 3 *10¯¹³. What is the concentration of the HAsO₄²¯ in a solution whose initial arsenic acid concentration was 0.35 M ?

A) 9.4 *10¯³ M
B) 2.5 * 10¯⁴ M
C) 8.8 *10¯⁵ M
D) 5.6 * 10¯⁸ M
E) None of these choices is correct.