Do "Lots for Sale" project in SPSS.
Follow the demo on my WEB page in the Samples Area.
Look at the "screen shots" to see how to do the calculations and the "What If".
Remember only properties 2, 3 and 11 should work.
Copy the raw data from the first 5 columns of Project 3 but without row 1, the row with the labels, into the SPSS window.