Which of the following trade restrictions would likely result in the least overall inefficiency?
a) A $20 tariff that resulted in 5000 unites of imports
b)A quota of 3000 units that has a licensing fee set at the difference between the world price and the domestic price after the quota takes effects
c) A $30 tariff that resulted in 3000 units of imports
d) A quota of 5000 units that does not have a licensing fee