The lengths of three sides of a trapezoid are shown below: side 1: 16z2 − 4z + 2 side 2: −2z + 21 + 7z2 side 3: 2 − 3z + 18z2 the perimeter of the trapezoid is 17z3 + 60z2 + 2z − 5. part a: what is the total length of sides 1, 2, and 3, of the trapezoid? (4 points) part b: what is the length of the fourth side of the trapezoid? (3 points) 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)