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:
| Masculine a-stems | Masculine u-stems | Feminine ō-stems | Neuter a-stems | Masculine an-stems | Feminine ōn-stems |
| --- | --- | --- | --- | --- | --- |
| fisker | sun | siang | skip | biti | vika |
| fisks | sunar | siangar | skips | bita | viku |
| fiski | syni | siangu | skipi | bita | viku |
| fisk | sun | siang | skip | bita | viku |
| fiskar | synir | siangar | skip | bitar | vikur |
| fiska | suna | sianga | skipa | bita | vikna |
| fiskum | sunum | siangum | skipum | bitum | vikum |
| fiska | syni | siangar | skip | bita | vikur |
Question:
What is the masculine u form for the old Swedish word with a neuter a form of skipum?
Answer:
sunum