That gross profit and corporate tax liability are mathematically related is a matter of common knowledge and accounting definition, as taxable income is derived directly from business earnings.
The claim states that gross profit and corporate tax liability are mathematically related. In accounting and tax law, corporate income taxes are fundamentally calculated as a function of a firm's profits (typically net profit, which originates from gross profit). This is a definitional and mathematical truism that does not require empirical citation, making it common knowledge.