Fix the variable name `stock_symbol`

app.py

@@ -18,14 +18,15 @@ def get_stock_price(stock_symbol: str)-> str:
             identify a publicly traded company's shares on a stock exchange, e.g., MSFT, AMZN.
 
     Returns:
-        current stock price in dollars.
+        one sentence which contains the current stock price in dollars if the Yahoo Finance API
+        call succeeds and one error message otherwise.
     """
     try:
         ticker = yf.Ticker(stock_symbol.upper())
         price = ticker.info["regularMarketPrice"]
-        return f"The current stock price of {symbol.upper()} is ${price:.2f}."
+        return f"The current stock price of {stock_symbol.upper()} is ${price:.2f}."
     except Exception as e:
-        return f"Failed to retrieve stock price for {symbol}: {str(e)}"
+        return f"Failed to retrieve stock price for {stock_symbol}: {str(e)}"
 
 @tool
 def get_current_time_in_timezone(timezone: str) -> str: