hello again everyone ><>< sorry but i need a bit more help

ABCD is a square of unit length and points Eand F are taken on the sides AB and AD respectively such that AE = AF = x

a) Express the area of the Quadrilateral CDFE as a function of x

b) Find the greatest area the quadrilateral can have

and if its not too much trouble can you please draw a diagram it would be most helpful