An Employee Who Produces 10 Components in an Hour Earns

An employee who produces 10 components in an hour earns $9 ($.90 X 10) per hour,while an employee who produces 15 components earns $13.50 ($.90 x 15) .This is an example of a:

A) commission plan.
B) differential piece rate plan.
C) direct commission plan.
D) profit sharing plan.
E) straight piecework plan.