a scuba diver breathing normal air descend to 100 m of depth, where the toal pressure is 11 atm. What is the partial pressure of oxygen that the diver experiences at this depth?

Question

I know that at 100m that a diver would have to breathe Heliox, meaning that the air in the tank is a combo of O2 and He.

But I don't know how to figure out the problem.

Assume it is not heliox, but atmospheric air. What percent of atmospheric pressure is the partial pressure of O2.

would that be 21%?