The nationally optimal tariff is the tariff for which : a. the production effect is equal to the consumption effect of the tariff . b. the government collects the highest tariff revenue. c. the difference between the government tariff revenue and the sum of consumption an d production effect is the highest . d. the difference between the part of the tariff paid by the ex port ers and the welfare loss associated with the consumpti on and production effect s is the highest .