Chapter 8, Problem 8.63SP

What hybridization would you expect for the indicated atom in each of the following ions?
(a) ${\text{BH}}_{\text{4}}{}^{-}$  (b) ${\text{HCO}}_{\text{2}}{}^{-}$
(c) ${\text{CH}}_{\text{3}}{}^{+}$  (d) ${\text{CH}}_{\text{3}}{}^{-}$