Is this an okay thing to ask current employer?

[confused]

I am accepting a per diem job offer which is at least 8 hours/week.  My current job is 20 hrs/week.  I can’t physically/mentally do both.  I am thinking on explaining the predicament to my boss and asking if I could cut my hours in half and work 10 hr/week.  I know she may say no, but   Should I ask?  I am not sure what I will do if she says no, probably give 2 weeks notice.

ETA. I asked and they can not reduce hours so I gave notice

Edited December 30, 2020 by confused

[sugarsugar]

I hope that’s a solution that works out for you. And hope the new job works out.