What was the difference between the high and low closing prices per share for common stock in the second quarter of 2019?
{"COMMON STOCK PRICES -- 2019": {"First Quarter": "First Quarter", "Second Quarter": "Second Quarter", "Third Quarter": "Third Quarter", "Fourth Quarter": "Fourth Quarter"}, "COMMON STOCK PRICES -- High": {"First Quarter": 15.4, "Second Quarter": 17.81, "Third Quarter": 16.4, "Fourth Quarter": 11.59}, "COMMON STOCK PRICES -- Low": {"First Quarter": 10.49, "Second Quarter": 13.76, "Third Quarter": 9.92, "Fourth Quarter": 8.09}}
high_2019 = df["COMMON STOCK PRICES -- High"]["Second Quarter"]
low_2019 = df["COMMON STOCK PRICES -- Low"]["Second Quarter"]
answer = high_2019 - low_2019