Calculate the run rate at the end of 17 overs of the match ID 335987 on 4/18/2008.
4/18/2008 refers to Match_Date = 4/18/2008; end of 17 overs refers to count(Toss_Name = 'field' ) = 17; run rate = divide(sum(Runs_Scored) when Toss_Name = 'bat', sum(Over_Id) when Toss_Name = 'field')
SELECT CAST(COUNT(CASE WHEN T1.Toss_Name = 'bat' THEN T3.Runs_Scored ELSE NULL END) AS REAL) / SUM(CASE WHEN T1.Toss_Name = 'field' THEN 1 ELSE 0 END) FROM Toss_Decision AS T1 INNER JOIN Match AS T2 ON T1.Toss_Id = T2.Toss_Decide INNER JOIN Batsman_Scored AS T3 ON T2.Match_Id = T3.Match_Id WHERE T2.Match_Id = 335987 AND T2.Match_Date = '2008-04-18' GROUP BY T3.Over_Id HAVING COUNT(T1.Toss_Name = 'field') = 17