Build iPhone Application

Hi, I would like an iPhone Game application created, all graphics will be provided on request of them. We want the graphics to be designed by us. The game is a tower defence game, it is pretty simple the objective is to stop units from the left hand side of the screen getting to the right hand side of the screen. The way to stop them is for the user on the iPhone to build towers on the map using the touch screen. There wants to be 3 modes: Easy, Medium and Hard. and 5 maps on each of the modes (maps/graphics will obviouslly be provided) and 150 levels on each just each time the enemy units trying to get across the screen get harder and harder, faster more of them etc. There wants to be 5 different towers you can build, each being upgradable on the map. Obviously the towers cost money to build and upgrade money is earned by destroying enemy units. If you need any more details on the project let me know. Kind Regards, Matt Lovett