Choco Co. provides DIY art frames and accessories. Choco Co. does not charge its customers for shipping charges on art frame orders and following is the shipping cost information for the last four months of 2016:

Month	Number of frames sold	Shipping costs
January	400	$10,000
February	500	$11,000
March	800	$12,000
April	600	$11,500

Using the high-low method, Choco Co.s total shipping cost can be estimated as following equation.

Total shipping cost = ( ) x number of frames sold) + ( )