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:
| Pump type and source | Typical use | 35 °C\n(e.g. heated screed floor) | 45 °C\n(e.g. heated screed floor) | 55 °C\n(e.g. heated timber floor) | 65 °C\n(e.g. radiator or DHW) | 75 °C\n(e.g. radiator and DHW) | 85 °C\n(e.g. radiator and DHW) |
| --- | --- | --- | --- | --- | --- | --- | --- |
| High-efficiency air source heat pump (ASHP), air at −20 °C |  | 2.2 | 2.0 | ‐ | ‐ | ‐ | ‐ |
| Two-stage ASHP, air at −20 °C | Low source temperature | 2.4 | 2.2 | 1.9 | ‐ | ‐ | ‐ |
| High efficiency ASHP, air at 0 °C | Low output temperature | 3.8 | 2.8 | 2.2 | 2.0 | ‐ | ‐ |
| Prototype transcritical CO\n2 (R744) heat pump with tripartite gas cooler, source at 0 °C | High output temperature | 3.3 | ‐ | ‐ | 4.2 | ‐ | 3.0 |
| Ground source heat pump (GSHP), water at 0 °C |  | 5.0 | 3.7 | 2.9 | 2.4 | ‐ | ‐ |
| GSHP, ground at 10 °C | Low output temperature | 7.2 | 5.0 | 3.7 | 2.9 | 2.4 | ‐ |
| Theoretical Carnot cycle limit, source −20 °C |  | 5.6 | 4.9 | 4.4 | 4.0 | 3.7 | 3.4 |
| Theoretical Carnot cycle limit, source 0 °C |  | 8.8 | 7.1 | 6.0 | 5.2 | 4.6 | 4.2 |
| Theoretical Lorentzen cycle limit (CO\n2 pump), return fluid 25 °C, source 0 °C |  | 10.1 | 8.8 | 7.9 | 7.1 | 6.5 | 6.1 |
| Theoretical Carnot cycle limit, source 10 °C |  | 12.3 | 9.1 | 7.3 | 6.1 | 5.4 | 4.8 |
Question:
how many pump types have no typical use listed?
Answer:
6