Suggest Treatment For Premature Graying Of Hair

hello, Dr. khanna , My name is Amit kumar 25 hair is turning white in the front top head at one place more than 100 hair have become white, white hair is spreading that aria day by day.what could be remedy for that to stop or turning black again pls doctor consult me good remedy for that hair transplant or what for that area and tell me the expected reasonable cost for the treatment..