Hey sitri.

Do you want the prices to be $22 for 6000, $25 for 3000 and all appropriate numbers in between?

If so we use what is called linear interpolation which gives us the result:

Price_Per_Square_Foot = mx + b where m = (25-22)/(3000-6000) = -1/1000 and b is found by calculating:

22 = -1/1000*6000 + b

25 = -1/1000*3000 + b

or

22 = -6 + b

25 = -3 + b or b = 28.

This means we now have a formula to calculate the price per square foot which is

Price = -1/1000*(total_square_feet) + 28 where total_square_feet is in between 3000 and 6000 inclusive.