How to find the area of an uneven quadrilateral?

Alright here is the question for the hw that im doing and still working on.....please explain in detail and give the full decimal approximations. The four sequential sides of a quadrilateral have lengths a=5.1 b=6.2 c=8.4 and d=11.4 (all measured in yards). THe angle between the two smallest sides is 106 degrees. What is the area of this figure?? Please give full decimal approximations!!!