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:
| TOPS design code | Electrical system | Max speed | Weight | Brakes | Route availability | Notes |
| --- | --- | --- | --- | --- | --- | --- |
| 08-0AV | 90 V | 20 mph (32 km/h) | 49.8 te (496 kN) | vacuum | 5 |  |
| 08-0BX | 110 V | 20 mph (32 km/h) | 50.4 te (502 kN) | dual | 5 |  |
| 08-0CA | 90 V | 20 mph (32 km/h) | 49.6 te (494 kN) | air | 5 |  |
| 08-0DV | 90 V | 15 mph (24 km/h) | 49.8 te (496 kN) | vacuum | 5 |  |
| 08-0BX | 90 V | 15 mph (24 km/h) | 50.4 te (502 kN) | dual | 5 |  |
| 08-0FA | 90 V | 15 mph (24 km/h) | 49.6 te (494 kN) | air | 5 |  |
| 08-0KX | 110 V | 15 mph (24 km/h) | 50.4 te (502 kN) | dual | 5 |  |
| 08-0LX | 110 V | 15 mph (24 km/h) | 50.4 te (502 kN) | dual | 5 | Scharfenberg adapter fitted |
| 08-0MA | 110 V | 15 mph (24 km/h) | 49.8 te (496 kN) | air | 5 |  |
| 08-0NA | 90 V | 15 mph (24 km/h) | 49.8 te (496 kN) | air | 5 | fitted with Buckeye couplings |
| 08-0PA | 90 V | 15 mph (24 km/h) | 51 te (508 kN) | air | 6 | fitted with Buckeye couplings |
| 08-0QA | 90 V | 15 mph (24 km/h) | 51 te (508 kN) | air | 6 | fitted with Buckeye couplings |
| 08-0RA | 110 V | 15 mph (24 km/h) | 51 te (508 kN) | air | 6 | fitted with Buckeye couplings |
| 08-0SA | 110 V | 15 mph (24 km/h) | 49 te (488 kN) | air | 6 |  |
Question:
how many have a max speed of 20 but are only dual brakes?
Answer:
1