5.2.4.21 Various problems on the plane

In the triangle \( A B C \) on the side \( A B \) the points \( K \) and \( L \) are chosen so that \( A K=K L=L B \), and on the side \( B C \) the points \( M \) and \( N \) are chosen so that \( B M: M N: N C= \) \( 1: 2: 1 \). Find the area of ​​the triangle \( A B C \) if it is known that the area of ​​the quadrilateral \( K L M N \) is 20.