Suppose a, b denote the distinct real roots of the quadratic polynomial x2+20x−2020 and suppose c,d denote the distinct complex roots of the quadratic polynomial x2−20x+2020 . Then the value ofac(a−c)+ad(a−d)+bc(b−c)+bd(b−d)is

x2+20x−2020=0 has two roots a,b∈Rx2−20x+2020=0 has two roots c,d∈ complex ac(a−c)+ad(a−d)+bc(b−c)+bd(b−d)=a2c−ac2+a2d−ad2+b2c−bc2+b2d−bd2=a2(c+d)+b2(c+d)−c2(a+b)−d2(a+b)=(c+d)a2+b2−(a+b)c2+d2=(c+d)(a+b)2−2ab−(a+b)(c+d)2−2cd=20(20)2+4040+20(20)2−4040=20(20)2+4040+(20)2−4040=20×800=16000