Independently, increasing the after-tax income of those likely to spend, rather than save, increases the demand for goods. Furthermore, even if the government knew that a market was operating under Bertrand competition, the home firm would generally oppose this policy, and in practice export taxes are rarely used. Sqrt(dblTimeTillExp) Nd1 = NormCDF(d1) Nd2 = NormCDF(d2) dblBSPrice = dblStock * Nd1 - dblStrike * _ Math.