with calculations

Cromarty Corp. mines granite. In Jan 2016 Cromarty purchased a mine for $17 million. Cromarty estimated the mine had reserves of 10 million tons of granite, and the residual value of land would be $1 million. In Jan 2021, after extracting 6 million tons, Cromarty revised the mine's total reserves up from 10 million to 12 million tons. However, the residual value was revise down to $0. Determine Cromarty's estimated cost per ton of granite as at Jan 1, 2021