Thanks, best of luck.
If its NOT the belt, you may just have a coincidence on your hands. Start by checking the fluid level in the Power Steering (it being low - actually more like out - might explain the lack of steering and brakes). If its gone, you might be able to get it running again just by topping it up, but it does not "use" fluid, it "loses" fluid, so you will need to get some leaks fixed or the pump replaced, though it MIGHT also be the hydro booster doing the leaking.
In this scenario, the battery might just be coincidentally getting weak, old, or low on water at the same time, or even the alternator doing the same thing.
All things considered, the serpentine belt would be the cheapest and easiest solution, so I hope that's it.
Best of luck!
"You can never be free until you let yourself go."