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:
| Rank | Heat | Name | Nationality | Result |
| --- | --- | --- | --- | --- |
| 1.0 | 3.0 | Melaine Walker | Jamaica | 54.46 |
| 2.0 | 4.0 | Ekaterina Bikert | Russia | 55.15 |
| 3.0 | 3.0 | Anastasiya Rabchenyuk | Ukraine | 55.18 |
| 4.0 | 2.0 | Tasha Danvers | Great Britain | 55.19 |
| 5.0 | 3.0 | Tsvetelina Kirilova | Bulgaria | 55.22 |
| 6.0 | 2.0 | Anastasiya Ott | Russia | 55.34 |
| 7.0 | 4.0 | Anna Jesień | Poland | 55.35 |
| 8.0 | 1.0 | Tiffany Ross-Williams | United States | 55.51 |
| 9.0 | 1.0 | Irina Obedina | Russia | 55.71 |
| 10.0 | 2.0 | Nickiesha Wilson | Jamaica | 55.75 |
| 11.0 | 1.0 | Satomi Kubokura | Japan | 55.82 |
| 12.0 | 4.0 | Zuzana Hejnová | Czech Republic | 55.91 |
| 13.0 | 3.0 | Queen Harrison | United States | 55.96 |
| 14.0 | 2.0 | Angela Morosanu | Romania | 56.07 |
| 15.0 | 2.0 | Sheena Tosta | United States | 56.12 |
| 16.0 | 3.0 | Aïssata Soulama | Burkina Faso | 56.37 |
| 17.0 | 1.0 | Shevon Stoddart | Jamaica | 56.52 |
| 18.0 | 2.0 | Nikolina Horvat | Croatia | 56.65 |
| 19.0 | 4.0 | Tatyana Azarova | Kazakhstan | 56.88 |
| 20.0 | 4.0 | Muna Jabir Adam | Sudan | 57.16 |
| 21.0 | 1.0 | Ieva Zunda | Latvia | 57.43 |
| 22.0 | 1.0 | Lucimar Teodoro | Brazil | 57.68 |
| 23.0 | 4.0 | Josanne Lucas | Trinidad and Tobago | 57.76 |
| 24.0 | 3.0 | Carole Kaboud Mebam | Cameroon | 57.81 |
| 25.0 | 2.0 | Michelle Carey | Ireland | 57.99 |
| 26.0 | 4.0 | Laia Forcadell | Spain | 58.64 |
| 27.0 | 3.0 | Galina Pedan | Kyrgyzstan | 1:00.31 |
Question:
What is the Heat of the Player with a Rank of 18 or less and Result of 55.15?
Answer:
4.0