True or Flase? In order to aid the poor, the government introduces a scheme whereby the first 1kg of butter a family buys is subsidised and the remaining amounts are taxed. consider a family which consumes butter and is made neither better off nor worse off as a result of this scheme. The total amount of tax it pays cannot exceed the subsidy it receives.

用画图的方法可以判断出是True，但是有没有办法用代数方法证明出来呢？