Transaction Costs Models Click on a model link below to view or download the model. The models with a .ltx extension are formatted for traditional LINDO, .lng and .lg4 for LINGO and .xls for What'sBest!. NUSBOY.lng PORTCOST.xls PRODMIX.lng PRODMIXWB.xls PORTAX.lng PORTFOLIO_TAX.xls PORTFOLIO_TRANS.xls TRANCOST.ltx