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  1. Final number from repeated operation ●●●○○ 50 ptsThe 97 numbers 491,492,493,…,4997\frac{49}{1}, \frac{49}{2}, \frac{49}{3}, \ldots, \frac{49}{97} are written on a blackboard. Repeatedly pick two numbers a,ba, b on the board and replace them by 2ab−a−b+12ab - a - b + 1 until only one number remains. Find the final number.
  2. Least number of factors giving 51/2010 ●●●●○ 100 ptsFind the least positive integer nn for which there exists a set {s1,s2,…,sn}\{s_1, s_2, \ldots, s_n\} consisting of nn distinct positive integers such that (1−1s1)(1−1s2)⋯(1−1sn)=512010.\left(1-\frac{1}{s_1}\right)\left(1-\frac{1}{s_2}\right)\cdots\left(1-\frac{1}{s_n}\right)=\frac{51}{2010}.