1) Calculate angles DAC and DBM ( ∠DAC = ∠MNC = ∠ENB ) ( ∠DBM = ∠EBN )
2) Find line segments MN and BN
3) Find the area of a triangle BNC
4) Find the area of a triangle BEN using the law of sines and Heron's formula.
Add these two areas ( BNC and BEN ) and you're done. 
( Btw, the above post is mine too
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