The following relational schema represents PRODUCT, SUPPLY, and SUPPLIER tables, where P# = Product Number, QTY = Quantity, S# = Supplier Number. SELL_PRICE in PRODUCT is the price of selling, while SUP_PRICE is the supplier-pnce supplied by the supplier. PRODUCT (P#, P_NAME, SELL PRICE, QTY) SUPPLY(S#*, P#*, SUP_PRICE) SUPPLIER(S#, CITY) The above contain an important error. What is it? Be specific. Explain.