A company purchases machinery costing $50,000 in October of 2006. Five years later they discover a better, more efficient machine they could purchase to replace the existing machine. The new machine costs $90,000 and the company has determined that they would be able to sell the original machine for $30,000. In making the decision about buying the new machine, how much are total sunk costs?
A. $60,000
B. $40,000
C. $50,000
D. $10,000