Adding 7 days or 5 days to datepicker

Adding 7 days or 5 days to datepicker

I am developing an mvc application with some datepicker textboxes and Radiobuttons.
What I need to do is, there is a dropdownlist box with values --Calendar or Business . When a user select a business and pick a date from the two datepicker textboxes,5 days should be added to start date so date difference between start date and End date should be 5 business days. When Calendar is selected, 7 days should be added to start date so the the date difference between start and End date should be 7 days. I can't  seem to get my JQuery to work. Any help will be appreciated

The html and Jquery can be found here