∀ {α : Type u_1} {β : Type u_2} [inst : MeasurableSpace α] [inst_1 : MeasurableSpace β] {μ : MeasureTheory.Measure α}
  {ν : MeasureTheory.Measure β} (s : Set α) (t : Set β), (μ.prod ν) (s ×ˢ t) ≤ μ s * ν t