2009 Ford Mustang FOB?

Hello - My wife has a 2009 Ford Mustang. When she tried to unlock the car with her FOB, it did not work, neither did the hatch release for the trunk or the alarm. I tried to use my FOB but had the same results, so I suspect it has nothing to do with the FOB, maybe something internal in the car. Anyone else have a problem like this, and would you be willing to share your solution, if there was one.

The car battery is probably dead.

Either the car battery is dead or the batteries in the fobs, or both.