What is the oxidation number of sulfur in $$\mathrm{H}_2 \mathrm{SO}_5$$ ?

Identify the elements undergoing reduction and oxidation respectively in the following redox reaction.

$$3 \mathrm{H}_3 \mathrm{AsO}_{3(\mathrm{aq})}+\mathrm{BrO}_{3(\mathrm{aq})}^{-} \rightarrow \mathrm{Br}_{(\mathrm{aq})}^{-}+3 \mathrm{H}_3 \mathrm{AsO}_4$$

What is the value of $$x$$ in order to balance following redox reaction?

$$\mathrm{Mn}_{(\mathrm{aq})}^{2+}+x \mathrm{ClO}_{3(\mathrm{aq})}^{-} \rightarrow \mathrm{MnO}_{2(\mathrm{~s})}+x \mathrm{ClO}_{2(\mathrm{aq})}$$

What is the oxidation state of carbon in $$\mathrm{CaC}_2$$ and $$\mathrm{K}_2 \mathrm{C}_2 \mathrm{O}_4$$ respectively?