During the whole song you don't really have to use your pinky on the b string 5th fret since the song is in a b arrangement. The song sounds fine with an open b (if not better) also the l the song is going to sound cleaner. I recommend this way if your just playing by yourself. Then you have an extra finger to spare to when you hit that B bass which is important you can also play A string second fret and D string second fret with one finger which makes that note sound a little better and then for the whole song you are only using three fingers instead of 5!. Try it!