syms Ca Cb Cc Cd Ce Cf

kD = 0.25;
kE = 0.1;
kF = 5.0;
Canot = 1.5;
Cbnot = 2.0;
tau = 5.0;

rD1 = kD*Ca*(Cb)^2;
rE2 = kE*Ca*Cd;
rF3 = kF*Cb*(Cc)^2;

rA = -rD1 - 3*rE2;
rB = -2*rD1-rF3;
rC = rD1-2*rF3+rE2;
rD = rD1-2*rE2+rF3;
rE = rE2;
rF = rF3;

Ca = Canot + rA*tau;
cB = Cbnot + rB*tau;
Cc = rC*tau;
Cd = rD*tau;
Ce = rE*tau;
Cf = rF*tau;