Join black yarn:
9. inc*6=12 sc
10. (1 sc, inc)*6=18 sc
Change to yellow yarn:
11-12. 18 sc
Change to black yarn:
13. 18 sc
14. (4 sc, dec)*3=15 sc
Change to yellow yarn:
15. (3 sc, dec)*3=12 sc
16. (2 sc, dec)*3=9 sc
Change to black yarn:
17. (1 sc, dec)*3=6 sc. Cut the yellow yarn.
18. dec*3. Cut the yarn and fix the end.
Crochet cap with black yarn:
1. 6 sc in AR
2. inc*6=12 sc
3. (1 sc, inc)*6=18 sc
4. (2 sc, inc)*6=24 sc
5-6. 24 sc