We can't. That is up to you to decide. In general, you can look around for the books of similar genre and their prices. There is a minimum price of the books on Pothi.com depending on the physical specifications of your book. The price can not be set below that. But beyond that, it is up to you to set the price. You can calculate the royalty you will earn at various price levels using Price and Royalty Calculator ("For Distribution" tab). If you think that you can command premium for the content of the book, you can price it high and earn more royalties.