East India Company manufactures henna-based products for shipment in cases around the world. The company notes the following information for overhead for daily production:

Volume	Total cost per case
860 cases	$12,000
880 cases	$13,000
1060 cases	$14,400

Utilizing the high-low method to determine the overhead cost formula for East India Company, the correct calculation is ________.

y = $1,680 + $12x

y = $14,400 + $1,680x

y = $1,680 + 1,060x

y = $12,720 + $12x