How much is it to fix a broken front facing camera on iphone 4

I have an iPhone 4 , not 4s, and I had dropped it in water previously, but it works completely except for my front facing camera, which is what I'm desperate to have again also how much does it cost to repair?, I don't even remember being able to use my front camera because its been broke for so long. (4 years I've had the phone, about 2 years with the broke camera)

PLEASE HELP, thankks