Single machine due-date scheduling of jobs with decreasing start-time dependent processing times

We study the problem of scheduling jobs whose processing times are decreasing functions of their starting times. We consider the case of a single machine and a common decreasing rate for the processing times. The problem is to determine an optimal combination of the due date and schedule so as to minimize the sum of due date, earliness and tardiness penalties. We give an O(n log n) time algorithm to solve this problem.