CCH Gold operates a gold mine in Western Australia. The manager of the company would like to better understand the cost structure of his business. Below is the information for the past three years of operations.

	2016	2017	2018
Production (tonnes of gold)	1,400	2,300	2,100
Straight-line depreciation	$400,000	$400,000	$400,000
Mining labour	$364,000	$598,000	$546,000
Royalties	$185,000	$207,500	$202,500
Trucking and hauling	$220,000	$310,000	$310,000
Charitable donations*	$35,000	$30,000	$40,000

(Note: Charity donations is a managerial decision that is unlikely to be related to changes in production.)

The Mining labour cost is:

Group of answer choices:

Committed Fixed Cost

Discretionary Fixed Cost

Variable cost

Semi-variable cost