Why B is True??

If D is inefficient technology, why people would choose it?

Al. The following technologies are available to produce 10 metres of cloth: Technology Number of Tonnes of coal worker days required A 15 3 B 10 2 C 3 4 D 4 5 (a) Technology A is preferred to technology C for any relative price of a worker days to a tonne of coal less than 1. Technology D is preferred to technology A for any relative prices of a worker days to a tonne of coal greater than 1, even though it is an inefficient technology. (c) B or D can be the optimally chosen technologies depending on the relative price of coal and workers. T TURN OVER