Lisa is buying potatoes at a grocery store. She can either spend $10$ dollars on a $25\text{-lb}$ bag or $15$ dollars on a $35\text{-lb}$ bag. Whic is the cheaper one? 
选项为:A:The $25\text{-lb}$ bag  B:The $35\text{-lb}$ bag  请回答其中一个选项.