If 50 mL of Oxygen gas is compressed from 20 atm of pressure to 40 atm of pressu What is the new volume at constant temperature?

Imagine that twenty i.u.’s of enzyme z were catalyzing the above reaction for one minute, under vmaxconditions, in a 3.00 ml assay volume. the assay is buffered with 20 mm phosphate buffer, ph 7.60. what will the ph be at the end of that one minute?