Thread: lebesgue measure

Assume f > g two measurable function on [a,b] and
E={(x,y) : g(x)≤y≤f(x), x ∈ [a,b]}
Show ∫ (f-g) dm = m×m E . that m is lebesgue measure.
(limits of integration is a,b)

help will be appreciated so much

Hint:Fubini Theorem