Completing the Square for Quadratics

Cassandra is selling cups of lemonade. So far, she has been selling each cup for $\$1$ and typically sells $80$ cups a day. $\\$ Cassandra is a smart entrepreneur and she knows that if she increases the price, less people will buy her lemonade. She finds that for every $\$0.25$ she raises the price, $10$ fewer cups will be bought. $\\$ Create a profit function for this scenario and find which price she should sell her cups of lemonade for in order to maximize the profit.