'3. 'lhe law of damrnrslung returns holds that a. the total product of an}; input must evenmalls' reach a maximum and fall as the employment of that input increases. h. the average product of an};r input must eventually reach a minimum and rise as the employment of all inputs increases proportionately. c. the marginal product of an]; input should eventually begin to decline as the employment of that input increases- d. the average product of an}? input should fall before it rises as the employment of that input increases