The debate about potato

Here's the item that sparked a 1minute debate in the supermarket on Saturday.


Ella> Hey, this Russet potato is 75cents per pound. But the 5pounds bag is $1.50 for the entire bag
Derrick> But we don't need 5 pounds of potatos, we just need 1-2 for the ABC soup that you are cooking.
JY> Erm.. This 1 potato is already 30cents, should we buy the 5pounds? Or better still, pay another 20 cents more for the 10 pounds bag. It's only $1.70 for the 10 pounds bag.
Derrick> No. Unless you are cooking something else using potatos.
JY> ok, let's just get the 1 potato.