Analytic solution for American strangle options using Laplace-Carson transforms

Abstract

A strangle has been an important strategy for options when the trader believes there will be a large movement in the underlying asset but are uncertain of which way the movement will be. In this paper, we derive analytic formula for the price of American strangle options. American strangle options can be mathematically formulated into the free boundary problems involving two early exercise boundaries. By using Laplace-Carson Transform(LCT), we can derive the nonlinear system of equations satisfied by the transformed value of two free boundaries. Then we solve this nonlinear system using Newton's method and finally get the free boundaries and option values using numerical Laplace inversion techniques. We also derive the value of perpetual American strangle options. Furthermore, We present various graphs for the free boundaries and option values according to the change of parameters.