Table:
text: 1987 German Grand Prix
Classification
Classification
Driver Constructor_ Laps Time_Retired Grid
Nelson Piquet Williams - Honda 44 1:21:25.091 4
Stefan Johansson McLaren - TAG 44 + 1:39.591 8
Ayrton Senna Lotus - Honda 43 + 1 Lap 2
Philippe Streiff Tyrrell - Ford 43 + 1 Lap 22
Jonathan Palmer Tyrrell - Ford 43 + 1 Lap 23
Philippe Alliot Lola - Ford 42 + 2 Laps 21
Alain Prost McLaren - TAG 39 Electrical 3
Martin Brundle Zakspeed 34 Not Classified 19
Piercarlo Ghinzani Ligier - Megatron 32 Engine 17
Adrián Campos Minardi - Motori Moderni 28 Engine 18
Thierry Boutsen Benetton - Ford 26 Engine 6

Question: How many laps are associated with a time of +1:39.591 for the 1987 German Grand Prix?

Question: What is the average number of laps for a starting grid of 6 in the 1987 German Grand Prix?