What is the percentage change in the weighted-average exercise price for options outstanding and exercisable in 2019 from 2018?
{"": {"Number of options": "(in thousands)", "Weighted-Average Exercise Price": ""}, "Outstanding and Exercisable at December 31, 2018": {"Number of options": 543.0, "Weighted-Average Exercise Price": 27.46}, "Exercised": {"Number of options": -6.0, "Weighted-Average Exercise Price": 11.38}, "Forfeited/Expired": {"Number of options": -68.0, "Weighted-Average Exercise Price": 24.78}, "Outstanding and Exercisable at December 31, 2019": {"Number of options": 469.0, "Weighted-Average Exercise Price": 28.04}}
weighted_average_exercise_price_2019 = df["Outstanding and Exercisable at December 31, 2019"]["Weighted-Average Exercise Price"]
weighted_average_exercise_price_2018 = df["Outstanding and Exercisable at December 31, 2018"]["Weighted-Average Exercise Price"]
answer = ( weighted_average_exercise_price_2019 - weighted_average_exercise_price_2018 ) / weighted_average_exercise_price_2018 * 100.0