Dropdown Option required in Hotel Booking Form

Hii,

I need a dropdown option in the backend of Hotel Booking so that we can use that whenever necessary. Suppose we need to insert 2 rates (Rs.3499/- for Double and Rs.3200/- for Single) for the same room. so in such case we need a dropdown option in the Hotel Booking Form associated with the room where if we select Double then Rs.3499/ will show and will be added to the cart after clicking on Booking Now Button and if we select Single then Rs.3200/- will show and will be added to the cart after clicking on Booking Now Button. Pl Help on this as early as possible because our Hotel Website Launching Date is coming nearer and is going to launch on 21st Jan 2018. So we have to add this dropdown option in the backend Hotel Booking before 20th Jan 2018.

Thank You

Thank You,
Aminul Huda