When setting performance measures for incentive systems, we can say that the best measures are those thatGroup of answer choicesa. are quantitative, simple to understand, and show a clear relationship to improved performance.b$.$ are qualitative, flexible, and create competition between employees.c$.$ allow employers to "ratchet up$"$ standards and base rewards on qualitative standards.d$.$ reduce administrative costs, determine rewards based only on quantity, and reward only exceptional employees.