A solution at standard conditions has {[H₃O⁺] = 2.00 x 10⁻⁶ or [OH⁻] = 2.00 x 10⁻⁶}. What is its {pH, pOH}?
a) -5.70
b) 5 x 10⁻⁹
c) 5.70
d) 8.30