Backend Developer for a cost calculator

UPDATE: My web developer wants it to be done by WordPress Plugins. Says scripting needs updates. Create a calculator plugin/code for WP using images steps. Should be compatible with latest Word Press. I am adding a roof cost calculator to my website. In order to calculate the cost, the client will fill out a FORM. The FORM is made of explanatory images and click buttons. They are: 1. What's your house area? - here the client writes the area 2. Is it one-story OR two-story house? - here the client makes the corresponding choice. 3. What is the slope of the roof - here the client make the corresponding choice The calculator will work like this: IF it is one-story house THEN house area is multiplied by roof slope multiplier(0.8 for low, 1.2 for medium, and 1.4 for high). The result is multiplied by 5.5( $5.5 per square foot). IF it is two-story house THEN house area is divided by two then multiplied by the slope multiplier. Again, the result is multiplied by 5.5. The " Calculate Cost" button probably will do the final multiplication( by 5.5) I'm uploading just a screenshot of the original design. It's being finalized by a freelancer at the moment. But I have the necessary files for the design images. layered working file, icons , transparent images etc