求助牛人几道当月机井

xld914

577.两个数，分别是x^r和y^s，问如果这两个数相等那么下面三点哪几点成立，1：x is multiple of y ; 2: y is multiple of x ; 3: r is multiple of s, 4:s is multiple of r

一个660的balance的minimum payment要大于600，有一个人他选择了一个balance的minimum payment超过了660，问这个balance是多少？
a，creditcard payment是200
b，creditcard payment占balance的25%