Only \( 2 \, \text{mL} \) of \( \text{KMnO}_4 \) solution of unknown molarity is required to reach the end point of a titration of \( 20 \, \text{mL} \) of oxalic acid (\( 2 \, \text{M} \)) in acidic medium. The molarity of \( \text{KMnO}_4 \) solution should be ______ \( \text{M} \).