What was the change in Cash generated from operations from 2018 to 2019?
{"Year ended 31 March": {"2019": "\u00a3m", "2018": "\u00a3m", "2017": "\u00a3m"}, "Cash generated from operations": {"2019": 4687, "2018": 5400, "2017": 6725}, "Tax paid": {"2019": -431, "2018": -473, "2017": -551}, "Net cash inflows from operating activities": {"2019": 4256, "2018": 4927, "2017": 6174}, "Net purchase of property, plant and equipment and software": {"2019": -3637, "2018": -3341, "2017": -3119}, "Free cash flow": {"2019": 619, "2018": 1586, "2017": 3055}, "Interest received": {"2019": 23, "2018": 7, "2017": 7}, "Interest paid": {"2019": -531, "2018": -555, "2017": -629}, "Add back pension deficit payments": {"2019": 2024, "2018": 872, "2017": 274}, "Add back net cash flow from specific items": {"2019": 598, "2018": 828, "2017": 205}, "Add back net sale of non-current asset investments": {"2019": 1, "2018": 19, "2017": -20}, "Add back prepayments in respect of acquisition of spectrum licence": {"2019": "-", "2018": 325, "2017": "-"}, "Remove refund on acquisition of spectrum licence": {"2019": -21, "2018": "-", "2017": "-"}, "Remove cash tax benefit of pension deficit payments": {"2019": -273, "2018": -109, "2017": -110}, "Normalised free cash flow b": {"2019": 2440, "2018": 2973, "2017": 2782}}
cash_generated_from_operations_2019 = df["Cash generated from operations"]["2019"]
cash_generated_from_operations_2018 = df["Cash generated from operations"]["2018"]
answer = cash_generated_from_operations_2019 - cash_generated_from_operations_2018