Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Driver | Constructor | Laps | Time/Retired | Grid |
| --- | --- | --- | --- | --- |
| Jackie Stewart | Tyrrell - Ford | 95.0 | 1:57:59.1 | 2.0 |
| Denny Hulme | McLaren - Ford | 95.0 | + 25.96 | 4.0 |
| Jacky Ickx | Ferrari | 95.0 | + 59.39 | 8.0 |
| Clay Regazzoni | Ferrari | 95.0 | + 1:06.72 | 6.0 |
| Tim Schenken | Surtees - Ford | 95.0 | + 1:09.11 | 11.0 |
| Ronnie Peterson | March - Ford | 94.0 | + 1 lap | 10.0 |
| Carlos Reutemann | Brabham - Ford | 93.0 | + 2 laps | 1.0 |
| Henri Pescarolo | March - Ford | 93.0 | + 2 laps | 15.0 |
| Howden Ganley | BRM | 93.0 | + 2 laps | 13.0 |
| Helmut Marko | BRM | 93.0 | + 2 laps | 19.0 |
| Niki Lauda | March - Ford | 93.0 | + 2 laps | 22.0 |
| Emerson Fittipaldi | Lotus - Ford | 61.0 | Suspension | 5.0 |
| François Cevert | Tyrrell - Ford | 59.0 | Gearbox | 7.0 |
| Reine Wisell | BRM | 59.0 | Water leak | 17.0 |
| Peter Revson | McLaren - Ford | 49.0 | Engine | 3.0 |
| Mario Andretti | Ferrari | 20.0 | Engine | 9.0 |
| Andrea de Adamich | Surtees - Ford | 11.0 | Fuel system | 14.0 |
| Graham Hill | Brabham - Ford | 11.0 | Fuel pump | 16.0 |
| Dave Walker | Lotus - Ford | 8.0 | Received outside assistance | 20.0 |
| Peter Gethin | BRM | 1.0 | Oil leak | 18.0 |
| Alex Soler-Roig | BRM | 1.0 | Accident | 21.0 |
| Chris Amon | Matra | 0.0 | Gearbox on warm-up lap | 12.0 |
Question:
How many grids does dave walker have?
Answer:
1.0