Hey, this is very easy, I will do it for free. You thank me later xD.
ok, the way to do it is using this formula:
SPL (DB) = 20xLog (p1/p0) ------> We know that P1= 0.25 Pa and P0 is 0,00002 (reference)
So the answer is:
SPL = 20XLog (0.25/0.00002)
SPL = 81.93 DB (82 dB rounding to the nearest dB as asked)
OK, thats it, if you need anything else just ask, if it is more complex I will set an offer. Sorry for my non perfect english, Im from Argentina.