For the reversible reaction
A ⇌ B (g)
in a closed container, the measured rate of the forward reaction is 0.12 mol·L⁻¹·min⁻¹, while the rate of the reverse reaction is 0.05 mol·L⁻¹·min⁻¹. The concentrations of A and B are still changing. Explain why the mixture is or is not at equilibrium.