What is the change in the increase in revenue in 2018 from 2017?
{"": {"2018": "(Dollars in millions)", "2017": ""}, "Increase in revenue": {"2018": 74, "2017": 49}, "Decrease in cost of sales": {"2018": 22, "2017": 15}, "Increase in loss on sale of business included in selling, general and administrative expense": {"2018": "\u2014", "2017": -102}, "Increase in depreciation expense (one-time)": {"2018": "\u2014", "2017": -44}, "Increase in depreciation expense (ongoing)": {"2018": -69, "2017": -47}, "Increase in interest expense": {"2018": -55, "2017": -39}, "Decrease in income tax expense": {"2018": 7, "2017": 65}, "Decrease in net income": {"2018": -21, "2017": -103}}
increase_in_revenue_2018 = df["Increase in revenue"]["2018"]
increase_in_revenue_2017 = df["Increase in revenue"]["2017"]
answer = increase_in_revenue_2018 - increase_in_revenue_2017