Stuck on formal proofs. Not sure how to continue

Question

I'm stuck on what how to continue. I know I'm missing a few steps but this is what I have so far. Thank you in advance!

1. ¬Cube(b) → Small(b)
2. Small(c) → (Small(d) ∨ Small(e))
3. Small(d) → ¬Small(c)

4. Cube(b) → ¬Small(e)

   5. Small(c)

      6. ¬Small(b)
         7. ¬Cube(b)
         8. Small(b) (→ Elim 1,7)
         9. ⊥ (⊥intro 6, 8)

      10.Cube(b) (¬Intro 7-9)

      11. ¬Small(e) (→ Elim 4,10)

Goal: Small(c) → Small(b)

Answer 1

12. $\qquad \qquad Small(d) \vee Small(e)$ ($\rightarrow $ Elim 2,5)

13. $\qquad \qquad \qquad Small(d)$

14. $\qquad \qquad \qquad Small(e)$

15. $\qquad \qquad \qquad \bot$ ($\bot$ Intro 11,14)

16. $\qquad \qquad\qquad Small(d)$ ($\bot $ Elim 15)

17. $\qquad \qquad Small(d)$ ($\vee $ Elim 12, 13-13, 14-16)

18. $\qquad \qquad \neg Small(c)$ ($\rightarrow$ Elim 17, 3)

19. $\qquad \qquad \bot $ ($\bot $ Intro 5,18)

20. $\qquad \neg \neg Small(b)$ ($\neg$ Intro 6-19)

21. $\qquad Small(b)$ ($\neg $ Elim 20)

22. $Small(b) \rightarrow Small(c)$ ($\rightarrow $ Intro 5-21)