invalid formula

This is my first stab at using this plugin and I am sure I am just doing something simple incorrectly but all I can get this to do is display invalid formula.

My formula is below:

(buffet+china+beverages+coffee+dessert)*guests+delivery

site is http://rwbaz.com/wordpress/catering/

Is is the formula or is it something else, I have literally spent hours on this no and to no avail, any help is appreciated.

http://wordpress.org/extend/plugins/jazzy-forms/