What is the change in Weighted-average grant date fair value between the options with two year vesting and three year vesting?
{"Volatility": {"Options with two year vesting": 57.5, "Options with three year vesting": 52.5}, "Dividend yield": {"Options with two year vesting": 10.0, "Options with three year vesting": 10.0}, "Risk-free interest rate": {"Options with two year vesting": 1.64, "Options with three year vesting": 1.65}, "Weighted-average grant date fair value": {"Options with two year vesting": 0.59, "Options with three year vesting": 0.58}}
weighted_average_grant_date_fair_value_options_with_two_year_vesting = df["Weighted-average grant date fair value"]["Options with two year vesting"]
weighted_average_grant_date_fair_value_options_with_three_year_vesting = df["Weighted-average grant date fair value"]["Options with three year vesting"]
answer = weighted_average_grant_date_fair_value_options_with_two_year_vesting - weighted_average_grant_date_fair_value_options_with_three_year_vesting