Complete parts (a) through (c) below. (a) At mail time, you receive a check for $24 and an envelope with neither a bill nor a check. What addition-by-0 fact has been illustrated? (b) At mail time, you receive a postcard from your friend and a bill for $28. What addition fact is illustrated? (c) What is illustrated if your mailbox has a bill for $19 and a check for $19? (a) At mail time, you receive a check for $24 and an envelope with neither a bill nor a check. What addition-by-0 fact has been illustrated? (Type an equation. Do not include the $ symbol in your answer. Do not simplify.)