If the pOH of a Ba(OH)2 solution is 1.88 at 25°C, what is the concentration (in M) of barium hydroxide?
a) 6.01 × 10⁻³ M
b) 3.00 × 10⁻³ M
c) 1.50 × 10⁻³ M
d) 7.50 × 10⁻³ M