Alanine is an amino acid that can have both equilibria in water: 

H₂N⎯CHCH₃⎯COOH + H₂O ⇌ ⁺H₃N⎯CHCH₃⎯COOH + OH^- K_b = 7.4x10⁻⁵

H₂N⎯CHCH₃⎯COOH + H₂O ⇌ H₂N⎯CHCH₃⎯COO^- + H₃O⁺ K_a = 4.5×10⁻³

It forms a zwitterion by intramolecular proton transfer 

H₂N⎯CHCH₃⎯COOH ⇌ ⁺H₃N⎯CHCH₃⎯COO^-

Determine the equilibrium constant for the reaction using the given K_a and K_b values