To the buyer who ordered 300 kg

To the buyer who ordered 300 kg

To the buyer, who ordered 300 kg of meat semi-finished products and paid 50% of their cost in accordance with the contract, the supplier received 500 kg of uncut meat. In accordance with the attached certificate, the sale of meat expired in two weeks.
What violations of the terms of the supply contract did the supplier make (quantity, quality, range, etc.)? What actions can the buyer take?

Additional information:

After payment you will be available a link to the solution of this problem in the file of MS Word. It should be noted that the problem solutions put up for sale were successfully handed over in the period 2003-2018 and could be outdated. However, the general algorithm will always remain true.