Costs that vary in total in direct proportion to changes in an activity level are called: Group of answer choices fixed costs sunk costs variable costs differential costs

variable costs

Explanation:

Fixed costs are costs that do not vary with output. e,g, rent, mortgage payments

If production is zero or if production is a million, Mortgage payments do not change - it remains the same no matter the level of output.  

Hourly wage costs and payments for production inputs are variable costs

Variable costs are costs that vary with production

If a producer decides not to produce any output, there would be no need to hire labour and thus no need to pay hourly wages.  

d,

answer; microeconomics;