dx1/dt=-b*x1*x4-d*x1+u1;
dx2/dt=b*q1*x1*x4-k1*x2-w1*x2;
dx3/dt=b*q2*x1*x4+k1*x2-w2*x3;
dx4/dt=-c*x4+k2*x3;
y1=x1;
y2=x4
