What was the percentage change in Extended warranty from 2018 to 2019?
{"": {"2019": "(in thousands)", "2018": ""}, "Maintenance, service and training": {"2019": 63815, "2018": 58362}, "Extended warranty": {"2019": 30677, "2018": 27422}, "Customer advances, undelivered elements and other": {"2019": 56358, "2018": 24677}, "Total deferred revenue and customer advances": {"2019": 150850, "2018": 110461}}
extended_warranty_2019 = df["Extended warranty"]["2019"]
extended_warranty_2018 = df["Extended warranty"]["2018"]
answer = ( extended_warranty_2019 - extended_warranty_2018 ) / extended_warranty_2018 * 100.0