Create a javascript calculator with dynamic layout

A calculator form which allows the total area of a series rectangles to be added and removed in order to calculate the total size. The calculator should be a single page which appears to be very simple allow the calculation of the area of a rectangle and then grows additional fields in responds to an 'add an area', 'subtract an area' control. Later in a separately commissioned phase will add the ability to e-mail the results. The area calculation should support calculation of a two sided area measured in feet, inches and common fractions of an inch down to 1/2,1/4,1/8,1/16. Subsequent areas can then be added and removed. The number of areas involved can be limited to 5 additions and 5 subtractions or 10 of either or not be limited. All rights to the resulting work and related works in all forms will be granted to us. Your work must be your own and not subject to existing licenses even public or open source licenses. The work may not incorporate copyrighted materials or copy the design of existing solutions other than solely owned by yourself and not otherwise licensed or sold.