Write SQL query to solve given problem: How much dollars was a Bitcoin worth on 2013/4/28 according to the coin market?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.market_cap FROM coins AS T1 INNER JOIN historical AS T2 ON T1.id = T2.coin_id WHERE T2.date = '2013-04-28' AND T1.name = 'Bitcoin'