Consider a consumer with strictly monotonic, strictly convex, and continuous preferences over two commodities: telephone calls and other goods. Suppose that currently the consumer has to pay an excise tax t on each telephone call. Let his current consumption bundle be $($x$1,$ x$2)$ so that his total tax equals tx$1($good $1$ is telephone calls and good $2$ is other goods$).$ Show that if the tax were removed and he had to pay a one$-$time fee equal to T $=$ tx$1$ instead $($the same amount but as a lump sum$),$ then he would be better off.