An important problem in thermodynamics is to find the work done by an ideal Carnot engine. A cycle consists of alternating expansion and compression of gas in a piston. The work done by the engine is equal to the area of the region $ R $ enclosed by two isothermal curves $ xy = a $, $ xy = b $ and two adiabatic curves $ xy^{1.4} = c $, $ xy^{1.4} = d $, where $ 0 < a < b $ and $ 0 < c < d $. Compute the work done by determining the area of $ R $.