Why must total income be identical to the dollar value of total output

Why must total income be identical to the dollar value of total output?

What will be an ideal response?

ANSWER

Total income must be identical to the dollar value of total output because spending by one person is income for another. Further, the definition of profit is important. Profit is the amount left over from total business receipts after all other costs have been paid. Hence, profit is the residual that makes total income equal to the dollar value of total output.