Given a substrate concentration of 5 mM, Vmax of 100 µmol/min, and Km of 10 mM, calculate the initial reaction velocity using the Michaelis-Menten equation.

• A. 50 µmol/min.
• B. 25 µmol/min.
• C. 33.33 µmol/min.
• D. 75 µmol/min.

Answer: (C)