What is the increase / (decrease) in inventories?
{"": {" million 2019": "", " million 2018": "(Restated)(a)"}, "Underlying operating profit before tax(b)": {" million 2019": 9947, " million 2018": 9463}, "Tax on underlying operating profit(c)": {" million 2019": -2536, " million 2018": -2432}, "Operating profit after tax": {" million 2019": 7411, " million 2018": 7031}, "Goodwill": {" million 2019": 18067, " million 2018": 17341}, "Intangible assets": {" million 2019": 12962, " million 2018": 12152}, "Property, plant and equipment": {" million 2019": 12062, " million 2018": 12088}, "Net assets held for sale": {" million 2019": 81, " million 2018": 108}, "Inventories": {" million 2019": 4164, " million 2018": 4301}, "Trade and other current receivables": {" million 2019": 6695, " million 2018": 6482}, "Trade payables and other current liabilities": {" million 2019": -14768, " million 2018": -14457}, "Period-end invested capital": {" million 2019": 39263, " million 2018": 38015}, "Average invested capital for the period": {" million 2019": 38639, " million 2018": 38749}, "Return on average invested capital": {" million 2019": 19.2, " million 2018": 18.1}}
inventories_2019 = df["Inventories"][" million 2019"]
inventories_2018 = df["Inventories"][" million 2018"]
answer = inventories_2019 - inventories_2018