How much was the increase in prepaid expenses from 2018 to 2019?
{"Prepaid expenses": {"2019": 137927, "2018": 90981}, "Prepaid income taxes .": {"2019": 47811, "2018": 59319}, "Indirect tax receivables .": {"2019": 29908, "2018": 26327}, "Restricted cash": {"2019": 13697, "2018": 19671}, "Notes receivable (1)": {"2019": 23873, "2018": 5196}, "Derivative instruments (2) .": {"2019": 1199, "2018": 2364}, "Other current assets": {"2019": 22040, "2018": 39203}, "Prepaid expenses and other current assets": {"2019": 276455, "2018": 243061}}
prepaid_expenses_2019 = df["Prepaid expenses"]["2019"]
prepaid_expenses_2018 = df["Prepaid expenses"]["2018"]
answer = prepaid_expenses_2019 - prepaid_expenses_2018