Simplify the expression: (10a2−4a)−(3a2+2a)(10a^2 - 4a) - (3a^2 + 2a)(10a2−4a)−(3a2+2a).
7a2−6a7a^2 - 6a7a2−6a
7a2−2a7a^2 - 2a7a2−2a
13a2−2a13a^2 - 2a13a2−2a
7a2+2a7a^2 + 2a7a2+2a