dx1/dt = -k3*x1 - x1*k7 + k4*x2 + u(t),
dx2/dt = (5*k5*x4*V36*x2 - 5*k5*S*V36^2*x2 - k5*R*x2*V3^2 + k5*x2*x3*V3 + k3*x1*V3 + x4*k6*V3 - k4*x2*V3 + k6*x3*V3) / (V3),
dx3/dt = k5*R*x2*V3 - k5*x2*x3 - k6*x3,
dx4/dt = (-5*k5*x4*V36*x2 + 5*k5*S*V36^2*x2 - x4*k6*V3) / (V3),
dx5/dt = x1*k7,
y1 = x5
