What was the change in total fair value for rights granted on 2 July 2017 to 2 July 2018?
{"Performance rights issued and outstanding at 30 June 2019 -- Grant Date": {"Vesting Date1": 1, "Fair Value per Right $": "Fair Value per Right $", "Rights Granted": "Rights Granted", "No. of Rights at 30/6/2019": 30}, "Performance rights issued and outstanding at 30 June 2019 -- 2 Jul 2017": {"Vesting Date1": 31.0, "Fair Value per Right $": 3.815, "Rights Granted": 355316.0, "No. of Rights at 30/6/2019": 355316.0}, "Performance rights issued and outstanding at 30 June 2019 -- 2 Jul 2018": {"Vesting Date1": 31.0, "Fair Value per Right $": 3.01, "Rights Granted": 530652.0, "No. of Rights at 30/6/2019": 530652.0}, "Performance rights issued and outstanding at 30 June 2019 -- Total": {"Vesting Date1": "", "Fair Value per Right $": "", "Rights Granted": 885968, "No. of Rights at 30/6/2019": 885968}}
fair_value_2018 = df["Performance rights issued and outstanding at 30 June 2019 -- 2 Jul 2018"]["Fair Value per Right $"]
rights_granted_2018 = df["Performance rights issued and outstanding at 30 June 2019 -- 2 Jul 2018"]["Rights Granted"]
fair_value_2017 = df["Performance rights issued and outstanding at 30 June 2019 -- 2 Jul 2017"]["Fair Value per Right $"]
rights_granted_2017 = df["Performance rights issued and outstanding at 30 June 2019 -- 2 Jul 2017"]["Rights Granted"]
answer = (fair_value_2018 * rights_granted_2018) - (fair_value_2017 * rights_granted_2017)