3. Let A = {n E N : 3 | n or 4 | n). Note that all numbers in A are positive. Determine whether the following four statements are true or false - explain your answers ("true" or "false" is not sufficient). (a) Fr E As.t. By E As.t. x+ y E A. "VORTIValA'VITA (q) (c) Fr E A s.t. Vy E A, x + y E A. (d) Vr E A, Vy E A, 3z ( As.t. xty + z EA