What is the percentage change for the end of period balance for Fulfillment Costs when comparing the beginning of period balance?
{"": {"Acquisition Costs": "(Dollars in millions)", "Fulfillment Costs": ""}, "Beginning of period balance": {"Acquisition Costs": 322, "Fulfillment Costs": 187}, "Costs incurred": {"Acquisition Costs": 208, "Fulfillment Costs": 158}, "Amortization": {"Acquisition Costs": -204, "Fulfillment Costs": -124}, "End of period balance": {"Acquisition Costs": 326, "Fulfillment Costs": 221}}
end_of_period_balance_fulfillment_costs = df["End of period balance"]["Fulfillment Costs"]
beginning_of_period_balance_fulfillment_costs = df["Beginning of period balance"]["Fulfillment Costs"]
answer = ( end_of_period_balance_fulfillment_costs - beginning_of_period_balance_fulfillment_costs ) / beginning_of_period_balance_fulfillment_costs * 100.0