∴S△ADE= 1/2S parallelogram ABCD (same base and equal height)
∴S△ABE+S△CDE= 1/2S parallelogram ABCD
∫AF//CD
∴S△CDF= 1/2S parallelogram ABCD (same base and equal height)
∴S△ABE+S△CDE=S△CDF=S △CEF+S△CDE
∴S△ABE=S△CEF = 10