What is the difference between sister's and sisters'?

For years, women’s professional golf was all but ignored. women’s tournaments received very little attention in the sports pages, but all that is changing. golfers like michelle wie are becoming almost as well-known as jordan spieth. the espn television channel covers major women’s tournaments. most impressive of all, the winnings on the women’s tour are getting downright hefty. top money for the recent founders cup in phoenix, arizona,was $225,000. who is michelle wie? what does the word hefty refer to? the national weather service has issued a winter storm warning for loudon and augusta counties beginning at 7: 00 p.m., est, friday, december 12, through 3: 00 a.m., est, sunday, december 14. snowfall of between 4 and 8 inches is predicted. school closings will be announced on channel 10 through the evening. how much snow is the storm likely to produce? what do you think est stands for?