The high-low method and least-squares regression are used by accountants to:

a. maximize output.

b. control operations.

c. estimate costs.

d. choose among alternative courses of action.

e. evaluate divisional managers for purposes of raises and promotions.

C. Estimate costs.

Explanation: High-low method of accounting is a managerial accounting system designed to separate the fixed costs from the variable costs from a limited amount of data.

The "least-square" method of regression analysis is a analytical method used in accounting, Statistical and mathematical calculations to determine the "line of best fit" in a given set of data, it also makes visual representation of the Relationship existing between data which are analysed.

C) Estimate costs