Find the domain of the vector functions, ????(????), listed below. using interval notation.

a) ????(????)=⟨ln(4????),????+19‾‾‾‾‾‾√,19−????‾‾‾‾‾√⟩
b) ????(????)=⟨????−9‾‾‾‾‾√,sin(2????),????2⟩
c) ????(????)=⟨ ????−9????,????????2−4‾‾‾‾‾‾√,????1/3⟩