Optimal stopping
The left side is increasing the right side decrasing soS=fxag,where
ais the solution of the equation( 1 +r)a=aF(a)+Z∞
axdF(x).One should sell atT 1 if
nmaxT 1 ξn^2 S=
nmaxT 1 ξna,
otherwise one should continue. We show thatτ=minnjmax
knξk 2 S^T=minnjmax
knξka