Phenylephrine (PE; See the Structure Below)is a Nasal Decongestant and Is

Phenylephrine (PE; see the structure below) is a nasal decongestant and is the active ingredient in Sudafed,which contains phenylephrine hydrochloride (PEHCl) .This conjugate acid of phenylephrine (PEH⁺) has a pK_a = 5.5.At a physiological pH of 7.4,what is the ratio of concentrations,[PE]/[PEH⁺]?

A) 6.7
B) 0.01
C) 0.14
D) 79
E) 21