Explain how to kill a mockingbird can be considered a problem novel. what is the problem and what does it reveal?

Which sentence is punctuated correctly? the shoes normally cost 40 dollars, however; we got them on sale. the shoes normally cost 40 dollars however we got them on sale. the shoes normally cost 40 dollars, however, we got them on sale. the shoes normally cost 40 dollars; however, we got them on sale.