打错了
A的效用是U1（X）=X

nash bargaining equilibirium:
U(X)=X,U(Y)=ln100+Y/100
the problem is:
Max U=U(X)U(Y) s.t.X+Y=500
FOC:
dU/dX=d(X(ln100+(500-X)/100)/dX=ln100+(500-X)/100+Xln100-X/100=ln100(1+X)+(500-2X)/100
let dU/dX=0
we have ln100(1+X)+(500-2X)/100=0
solve this equation, you will have a solution of X*
Since X+Y=500, you can have Y*.
(X*,Y*) is the nash bargaining equilibirium