The lengths of three sides of a trapezoid are shown below: side 1: 11z2 − 4z + 2 side 2: −2z + 3 + 12z2 side 3: 3 − 3z + 13z2 the perimeter of the trapezoid is 5z3 + 40z2 + 7z − 15. part a: what is the total length of sides 1, 2, and 3, of the trapezoid? part b: what is the length of the fourth side of the trapezoid? part c: do the answers for part a and part b show that the polynomials are closed under addition and subtraction? justify your answer. (3 points)