Unit Price Calculator

Would like to have a unit price calculator tool built in to the app. I.e. 6 rolls of toilet paper for $9 = $1.50 per roll.

Put in multiple lines so comparisons can be made. I.e. 10 rolls of toilet paper for $13.49 = $1.35 per roll, so it ranks as #1 best price and the 6 rolls for $9 ranks as #2, etc.

Allow to sort by price per unit (best value), save comparisons, assign a list of items to a store and tell me which store has the lowest overall price for all items, etc.