Fogel (1964) came up with two estimates of social savings ( and 

Fogel (1964) came up with two estimates of social savings ( and ). What do they represent?

(a) The level of industrial productivity using railroads and the level not using railroads
(b) The lowered benefit of transport for agricultural goods using railroads and the lowered benefit of transport for all goods and passengers using railroads
(c) The lower output of the U.S. economy using transportation financed through domestic capital and foreign capital
(d) The cost of shipping goods by railroads and the cost of shipping by waterways and wagon transport

ANSWER

(d)