In 2013, the AGI floor for someone under age 65 is 10% of AGI. The 7.5% floor applies to those 65 or older. Since it is you, and not your mom, who is taking the deduction, you must use the 10%-of-AGI floor.
A statutory term describing the cost used to determine your profit or loss from a sale or exchange of property. It is generally your original cost, increased by capital improvements, and decreased by depreciation, depletion, and other capital write-offs.