The following are the weights (in pounds) of ten people: $100,115, 135, 140, 180, 197, 203, 230, x, y$ (not necessarily in increasing order). It is also given that the average weight of these ten people is $157$ pounds, and there is a unique mode of $135$. Find the $56$-th percentile. 
选项为:A:$$100$$  B:$$115$$  C:$$125$$  D:$$135$$  请回答其中一个选项.