Question 1127456
This is a right triangle, and a 7-24-25 right triangle doubled (14-48-50) would have perimeter 112.  

MN is between the midpoints and is half of the base, which is 14.
That makes MN 7 
The quadrilateral is a trapezoid with base 1 14 and base 2 7; height is 12
Area would be (1/2)24(21)=252 square units.