What was the percentage change in cost of software under development between 2018 and 2019?
{"Movements": {"Rights and licenses": 0, "Internally generated software": 0, "Software under development": 0, "Total": 0}, "At 30 June 2019 -- Cost": {"Rights and licenses": 13, "Internally generated software": 12961, "Software under development": 16284, "Total": 29259}, "At 30 June 2019 -- Accumulated amortisation": {"Rights and licenses": "-", "Internally generated software": -5580, "Software under development": "-", "Total": -5580}, "At 30 June 2019 -- Netbook amount": {"Rights and licenses": 13, "Internally generated software": 7381, "Software under development": 16284, "Total": 23678}, "30 June 2018 -- Opening net book amount at 1 July 2017": {"Rights and licenses": 43, "Internally generated software": 442, "Software under development": 8053, "Total": 8538}, "30 June 2018 -- Additions  externally acquired": {"Rights and licenses": 13, "Internally generated software": "-", "Software under development": 5253, "Total": 5266}, "30 June 2018 -- Additions  internally developed": {"Rights and licenses": "-", "Internally generated software": "-", "Software under development": 1256, "Total": 1256}, "30 June 2018 -- Amortisation": {"Rights and licenses": -43, "Internally generated software": -1746, "Software under development": "-", "Total": -1789}, "30 June 2018 -- Transfers": {"Rights and licenses": "-", "Internally generated software": 7563, "Software under development": -7563, "Total": "-"}, "30 June 2018 -- Transfer between classes": {"Rights and licenses": "-", "Internally generated software": 744, "Software under development": "-", "Total": 744}, "30 June 2018 -- Disposals": {"Rights and licenses": "-", "Internally generated software": -618, "Software under development": -490, "Total": -1108}, "30 June 2018 -- Closing net book amount": {"Rights and licenses": 13, "Internally generated software": 6385, "Software under development": 6509, "Total": 12907}, "At 30 June 2018 -- Cost": {"Rights and licenses": 104, "Internally generated software": 9555, "Software under development": 6509, "Total": 16168}, "At 30 June 2018 -- Accumulated amortisation": {"Rights and licenses": -91, "Internally generated software": -3170, "Software under development": "-", "Total": -3261}, "At 30 June 2018 -- Net book amount": {"Rights and licenses": 13, "Internally generated software": 6385, "Software under development": 6509, "Total": 12907}}
cost_2019 = df["At 30 June 2019 -- Cost"]["Software under development"]
cost_2018 = df["30 June 2018 -- Closing net book amount"]["Software under development"]
answer = (cost_2019 - cost_2018) / cost_2018 * 100.0