Tell me the sum of cars per set for operator of london midland
Class Operator No. Built Year Built Cars per Set
British Rail Class 153
1017883
text text real text real
2-1017883-1
Fleet
Fleet
Class 153 Arriva Trains Wales 70 1991–1992 1
Class 153 East Midlands Trains 70 1991–1992 1
Class 153 London Midland 70 1991–1992 1
Class 153 Greater Anglia 70 1991–1992 1
Class 153 Northern Rail 70 1991–1992 1
Class 153 First Great Western 70 1991–1992 1
SELECT SUM Cars per Set FROM table WHERE Operator = london midland
london midland