What is the percentage amount of Bitcoin revenue among the total net revenue in 2018?
{"Transaction-based revenue": {"2018": 2471451, "2017": 1920174, "2016": 1456160}, "Starbucks transaction-based revenue": {"2018": "\u2014", "2017": "\u2014", "2016": 78903}, "Subscription and services-based revenue": {"2018": 591706, "2017": 252664, "2016": 129351}, "Hardware revenue": {"2018": 68503, "2017": 41415, "2016": 44307}, "Bitcoin revenue": {"2018": 166517, "2017": "\u2014", "2016": "\u2014"}, "Total net revenue": {"2018": 3298177, "2017": 2214253, "2016": 1708721}}
bitcoin_revenue_2018 = df["Bitcoin revenue"]["2018"]
total_net_revenue_2018 = df["Total net revenue"]["2018"]
answer = bitcoin_revenue_2018 / total_net_revenue_2018 * 100.0