Table:
text: 1976 Brazilian Grand Prix
Classification
Classification
Driver Constructor_ Laps Time_Retired Grid
Carlos Reutemann Brabham - Alfa Romeo 37 Out of Fuel 15
Emerson Fittipaldi Fittipaldi - Ford 37 + 3 Laps 5
Lella Lombardi March - Ford 36 + 4 Laps 22
Jean-Pierre Jarier Shadow - Ford 33 Accident 3
James Hunt McLaren - Ford 32 Accident 1
Vittorio Brambilla March - Ford 15 Oil Leak 7
Jacques Laffite Ligier - Matra 14 Transmission 11
Ronnie Peterson Lotus - Ford 10 Accident 18
Mario Andretti Lotus - Ford 6 Accident 16
John Watson Penske - Ford 2 Fuel System 8
Ian Ashley BRM 2 Oil Pump 21

text: 1976 Brazilian Grand Prix
Classification
Classification
Driver Constructor_ Laps Time_Retired Grid
Niki Lauda Ferrari 40 1:45:16.78 2
Patrick Depailler Tyrrell - Ford 40 + 21.47 9
Tom Pryce Shadow - Ford 40 + 23.84 12
Hans-Joachim Stuck March - Ford 40 + 1:28.17 14
Jody Scheckter Tyrrell - Ford 40 + 1:56.46 13
Jochen Mass McLaren - Ford 40 + 1:58.27 6
Clay Regazzoni Ferrari 40 + 2:15.24 4
Jacky Ickx Wolf-Williams - Ford 39 + 1 lap 19
Renzo Zorzi Williams - Ford 39 + 1 lap 17
Carlos Pace Brabham - Alfa Romeo 39 + 1 Lap 10
Ingo Hoffmann Fittipaldi - Ford 39 + 1 Lap 20

Question: What is the average laps for the grid less than 21 for Renzo Zorzi at the 1976 Brazilian Grand Prix?