"It is chiefly concerned with the following question: how should interest charges on goods in transit be computed when the goods travel close to the speed of li

"It is chiefly concerned with the following question: how should interest charges on goods in transit be computed when the goods travel close to the speed of light? This is a problem because the time taken in transit will appear less to an observer travelling with the goods than to a stationary observer. A solution is derived from economic theory, and two useless but true theorems are proved."