An article in the wall street journal describes one investment strategy that involves buying stocks on the london stock exchange at the beginning of november, selling them at the end of april, and then buying them again at the beginning of the following november. according to one investment analyst, this open double quotehalloween effectclose double quote investment strategy will earn an above-average return. the article notes that the analyst's open double quoteresults exclude transactions costs and taxes. close double quote source: corrie driebusch and aaron kuriloff, open double quotesell stocks in may? tempting but not very smart, close double quote wall street journal, may 1, 2016. how does the exclusion of transaction costs affect the returns cited due to the open double quotehalloween effectclose double quote? a. excluding transaction costs has no effect on the return. b. the effect of excluding transaction costs varies. c. excluding transaction costs understates the return. d. excluding transaction costs overstates the return.