function r =sol(x1,x2,t)
  r = -1/100*(-2147*exp(140*x1^(1/2))*x1^(1/2)+2147*x1^(1/2)+100*x2*exp(x1^(1/2)*t)+100*x2*exp(-x1^(1/2)*(-140+t)))/x1^(1/2)/(exp(140*x1^(1/2))-1);