dx1/dt = -b1*b0*x1*x4*x2 - b0*x1*x2 - x1*mu + mu + g*x3;
dx2/dt = -nu*x2 + b1*b0*x1*x4*x2 + b0*x1*x2 - mu*x2;
dx3/dt = nu*x2 - mu*x3 - g*x3;
dx4/dt = -M*x5;
dx5/dt = M*x4;
y1 = x2;
y2 = x3
