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:
| [A] (mol/L) | [H 3 PO 4 ]/[A] (%) | [H 2 PO 4 − ]/[A] (%) | [HPO 4 2− ]/[A] (%) | [PO 4 3− ]/[A] (%) |
| --- | --- | --- | --- | --- |
| 1 | 91.7 | 8.29 | 6.20×10 −6 | 1.60×10 −17 |
| 10 −1 | 76.1 | 23.9 | 6.20×10 −5 | 5.55×10 −16 |
| 10 −2 | 43.1 | 56.9 | 6.20×10 −4 | 2.33×10 −14 |
| 10 −3 | 10.6 | 89.3 | 6.20×10 −3 | 1.48×10 −12 |
| 10 −4 | 1.30 | 98.6 | 6.19×10 −2 | 1.34×10 −10 |
| 10 −5 | 0.133 | 99.3 | 0.612 | 1.30×10 −8 |
| 10 −6 | 1.34×10 −2 | 94.5 | 5.50 | 1.11×10 −6 |
| 10 −7 | 1.80×10 −3 | 74.5 | 25.5 | 3.02×10 −5 |
| 10 −10 | 8.24×10 −4 | 61.7 | 38.3 | 8.18×10 −5 |
Question:
What's the [A] when the H2PO 4 is 61.7?
Answer:
10 −10