How did they get the total for the apportioned cost??

Doran Realty Company purchased a plot of ground for $900,000 and spent $3,100,000 indeveloping it for building lots, The lots were classified into Highland, Midland and Lowlandgrades, to sell at $120,000, $90,000, and $60,000 each, respectively. InstructionsComplete the table below to allocate the cost of the lots using a relative sales value method