5.2.4.41 Various Problems on the Plane

Condition: in the triangle \ (a b c \) on the side \ (a b \) the point \ (m \) is selected, and on the side \ (a c \) point \ (n \). Sifts \ (c m \) and \ (b n \) intersect at point \ (k \). What is the area of the triangle \ (a m n \) if \ (b k: k n = 9: 4 \), the area of the triangle \ (b k c \) is 6/13, and the area of the triangle \ (m k n \) is \ (36 /247? \)