As this is a homework problem, you need to show your best effort to work the problem as far as you can. Include any assumptions you are making. That will let us see what your line of thinking is and where you might be going off track. We can then try to steer you back on track.

 

I had to think twice about the use of the term “support” in part ii. I think “withstand“ is the term I would choose,

 

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Start by drawing a graph of the voltage across L1. Then make use of the fact that the average voltage across an inductor is zero in the steady state.