Table:
text: 1971 French Grand Prix
Classification
Classification
Driver Constructor_ Laps Time_Retired Grid
Tim Schenken Brabham - Ford 50 Oil Pressure 14
François Mazet March - Ford 50 + 5 Laps 23
Max Jean March - Ford 46 Not Classified 22
Henri Pescarolo March - Ford 45 Gearbox 18
Graham Hill Brabham - Ford 34 Oil Pipe 4
Andrea de Adamich March - Alfa Romeo 31 Engine 20
Pedro Rodríguez BRM 27 Ignition 5
Clay Regazzoni Ferrari 20 Accident 2
Ronnie Peterson March - Alfa Romeo 19 Engine 12
Denny Hulme McLaren - Ford 16 Ignition 11
Jacky Ickx Ferrari 4 Engine 3
Alex Soler-Roig March - Ford 4 Fuel Pump 21

Question: What is the starting grid when the time/retirement is oil pressure and the laps for the 1971 French Grand Prix are 50+?