The fishing problem The decisions at times after the initial on d. The risk-free rate is set arbitrarily at first. Yes, there is an arbitrage: buy security 2 and subtract the same amount of security 1. Ginger Sevilla. Sigma estimation Using the spreadsheet implementation of the previous exerdse, we adjust O»by trial and error to obtain the give call premium. In this case the maximum was obtained in the first portion of the maximization, meaning that the trees should be harvested. Swaps Fig.