make possible comparison sentaces in cimprative and superlative degree ( nina’s book is rp 3000,rido’s book is rp 5000,andi’s book is rp 8000)

Nina's book is the cheapest among them.
Nina's book is cheaper than Rido's book.
Rido's book is cheaper than Andi's book.
Andi's book is the most expensive among them.