What Is the [H₃O⁺] in a Buffer That Consists of 0.30

Multiple Choice

What is the [H₃O⁺] in a buffer that consists of 0.30 M HCOOH and 0.20 M HCOONa? For HCOOH, K_a = 1.7 * 10¯⁴

A) 1.1 * 10¯⁴ M
B) 2.6 *10¯⁴ M
C) 4.3* 10¯⁴ M
D) 6.7 *10¯⁵ M
E) None of these choices is correct.