genetic algorithm- need help

i want to determine the value of constant k1 in the following equation dmc/dt = -k1*mc + coalinput;

i tried implementing using this code: mc(k,1)=mc(k-1,1)+T.*(-k1*mc(k-1,1)+coalinput);

but i dnt get the output. how to determine the value of k1. pls help.