An Enzymatic Reaction Has a V_max of 100 $\mu$ M/min at a Substrate Concentration of 5

Multiple Choice

An enzymatic reaction has a V_max of 100 $\mu$ M/min. At a substrate concentration of 5 $\mu$ M, the velocity is 25 $\mu$ M/min. What is the K_M for the reaction?

A) 5 $\mu$ M
B) 10 $\mu$ M
C) 15 $\mu$ M
D) 20 $\mu$ M
E) none of the above