The `buy()` function allows users to purchase multiple NFTs by paying USDT, with the amount calculated based on the price of the most recent NFT. However, when users purchase multiple NFTs, some NFTs may have different prices. This is because the `getPrice()` returns different prices based on different token ID ranges. Additionally, the price of the NFTs being purchased should be based on the current minting price, not the price of the most recently minted NFT. ```solidity uint256 price = getPrice(collection.minted()); uint256 cost = quantity * price; ... function getPrice(uint256 tokenId) public pure returns (uint256) { if(tokenId < 500) { return 300 * 1e6; } else if(tokenId >= 500 && tokenId < 2000) { return 450 * 1e6; } else if(tokenId >= 2000 && tokenId < 3000) { return 600 * 1e6; } else if(tokenId >= 3000 && tokenId < 4000) { return 800 * 1e6; } else if(tokenId >= 4000 && tokenId < 5000) { return 1000 * 1e6; } else if(tokenId >= 5000 && tokenId < 6000) { return 1200 * 1e6; } else if(tokenId >= 6000 && tokenId < 7000) { return 1400 * 1e6; } else if(tokenId >= 7000 && tokenId < 8000) { return 1600 * 1e6; } else if(tokenId >= 8000 && tokenId < 9000) { return 1800 * 1e6; } else if(tokenId >= 9000 && tokenId < 10000) { return 2000 * 1e6; } else if(tokenId >= 10000 && tokenId < 11000) { return 2200 * 1e6; } else if(tokenId >= 11000 && tokenId < 12000) { return 2400 * 1e6; } else if(tokenId >= 12000 && tokenId < 13000) { return 2600 * 1e6; } else if(tokenId >= 13000 && tokenId < 14000) { return 2800 * 1e6; } else if(tokenId >= 14000 && tokenId < 15000) { return 3000 * 1e6; } else if(tokenId >= 15000 && tokenId < 16000) { return 3200 * 1e6; } else if(tokenId >= 16000 && tokenId < 17000) { return 3400 * 1e6; } else if(tokenId >= 17000 && tokenId < 18000) { return 3600 * 1e6; } else if(tokenId >= 18000 && tokenId < 19000) { return 3800 * 1e6; } else if(tokenId >= 19000 && tokenId < 20000) { return 4000 * 1e6; } return 9999 * 1e6; } ```