Table:
text: 1986 Brazilian Grand Prix
Classification
Classification
Driver Constructor_ Laps Time_Retired Grid
Thierry Boutsen Arrows - BMW 37 Exhaust 15
Michele Alboreto Ferrari 35 Fuel System 6
Alain Prost McLaren - TAG 30 Engine 9
Christian Danner Osella - Alfa Romeo 29 Engine 24
Stefan Johansson Ferrari 26 Brakes 8
Patrick Tambay Lola - Hart 24 Battery 13
Riccardo Patrese Brabham - BMW 21 Water Leak 10
Jonathan Palmer Zakspeed 20 Engine 21
Marc Surer Arrows - BMW 19 Engine 20
Alessandro Nannini Minardi - Motori Moderni 18 Clutch 25
Andrea de Cesaris Minardi - Motori Moderni 16 Turbo 22
Piercarlo Ghinzani Osella - Alfa Romeo 16 Engine 23
Keke Rosberg McLaren - TAG 6 Engine 7

Question: How many laps did starting 15th at the 1986 Brazilian Grand Prix before ending with a period of exhaustion?