What is the ratio of the highest and lowest temperature in store 11?
store 11 refers to store_nbr = 11; highest temperature refers to Max(tmax); lowest temperature refers to Min(tmin); ration = Divide (Max(tmax), Min(tmin))
SELECT CAST((MAX(T1.tmax) - MIN(T1.tmin)) AS REAL) / MIN(T1.tmin) FROM weather AS T1 INNER JOIN relation AS T2 ON T1.station_nbr = T2.station_nbr WHERE T2.store_nbr = 11