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:
| Name | Country | Type | Moving from | Transfer window | Transfer fee |
| --- | --- | --- | --- | --- | --- |
| Bruzzese | BEL | Transferred | RFC Liège | Summer | Undisclosed |
| Schollen | BEL | Transferred | NAC Breda | Summer | Undisclosed |
| Triguinho | BRA | 6-month loan | São Caetano | Summer | n/a |
| Polák | CZE | Transferred | 1. FC Nürnberg | Summer | €3.5m |
| Théréau | FRA | Transferred | SteauaBucurești | Summer | €2.9m |
| Gillet | BEL | Transferred | Gent | Winter | About €2m |
| Chatelle | BEL | Transferred | Genk | Winter | Undisclosed |
| Iakovenko | UKR | 6-month loan | Genk | Winter | n/a |
| Pieroni | BEL | 6-month loan | Lens | Winter | n/a |
| Vlček | CZE | Transferred | Slavia Prague | Winter | Undisclosed |
Question:
Name the transfer fee with a transfer window of summer for schollen
Answer:
Undisclosed