What was the average Other expense, net for 2018 and 2019?
{"": {"2019": "", "2018": "(dollars in thousands)", "$": "", "%": ""}, "Other expense, net": {"2019": 4597.0, "2018": 4628.0, "$": -31.0, "%": -0.7}, "% of revenue": {"2019": 2, "2018": 3, "$": "", "%": ""}}
other_expense_net_2019 = df["Other expense, net"]["2019"]
other_expense_net_2018 = df["Other expense, net"]["2018"]
percent_of_revenue_2019 = df["% of revenue"]["2019"]
answer = ( other_expense_net_2019 + other_expense_net_2018 ) / percent_of_revenue_2019