The four angles of a quadrilateral are in the ratio 4 : 5 : 3 : 6. The difference between the greatest and the smallest angles of the quadrilateral is:

If the adjacent sides and opposite sides of a quadrilateral are equal but the diagonals are unequal, then it is a:

One of the angles of a parallelogram is 42°. What is the sum of half of the smallest angle and double of the greatest angle of the parallelogram?