∵ABCD is a parallelogram.

∴ The distance from point D and point C to side AB is equal.

That is to say, on the blast furnace side, the heights of △CBF and △DBF are equal.

Equal height at the same base

∴S△CBF=S△DBF

∴S△CBF-S△EBF=S△DBF-S△EBF

∴S△DBE=S△CEF

∵△ABE and △DBE have the same height at the bottom, and S△ABE=S△DBE.

∴S△ABE=S△CEF