Rectify the following errors.

(a) Credit Sales to Mohan Rs. 7,000 were recorded in purchase book.
(b) Credit Purchase from Rohan Rs. 9,000 were recorded in the sales book.
(c) Goods returned to Rakesh Rs. 4,000 were recorded in the sales return book.
(d) Goods returned from Mahesh Rs. 1,000 were recorded in purchase return book.