The Decomposition of a Solution of Hydrogen Peroxide, H₂O₂, Was

The decomposition of a solution of hydrogen peroxide, H₂O₂, was monitored over several days. Initially, hydrogen peroxide was present at a concentration of 1 mol L^-1; after four days the hydrogen peroxide was present at a concentration of 0.5 mol L^-1. What is the rate of the reaction for the decomposition of hydrogen peroxide?

A) 1.40*10^-6 mol L^-1
B) 1.40 * 10^-9 mol L^-1 s^-1
C) 1.40* 10^-6 mol L^-1 s^-1
D) 1.25 *10^-1 mol L^-1 day^-1
E) 8.68 * 10^-5 mol L^-1 min^-1