Database: formula_1
Question: Paul di Resta was in the No. 853 race, what percent faster did he finish in the 853rd race than the next race for the fastest lap speed?
SQL: SELECT (SUM(IIF(T2.raceId = 853, T2.fastestLapSpeed, 0)) - SUM(IIF(T2.raceId = 854, T2.fastestLapSpeed, 0))) * 100 / SUM(IIF(T2.raceId = 853, T2.fastestLapSpeed, 0)) FROM drivers AS T1 INNER JOIN results AS T2 ON T2.driverId = T1.driverId WHERE T1.forename = 'Paul' AND T1.surname = 'di Resta'