A print shop needs a compact invoice for posters. The starter already calculates total; change only the placeholder message assignments. Prefix each string with f so braces insert live variable values. Use {total:.2f} to show two decimal places in the price. The supplied print calls display your messages.
Edit main.py, press Run to inspect the two invoice lines, then Submit.
heading with an f-string to 4 posters for the art fair, using quantity and event.payment_line with an f-string to Due: $10.00, using total formatted to two decimal places.