$\mathrm{tr}(A) = 3 + (4-2i) + (4+2i) = 11$, which is real

$\det(A) = 3(4-2i)(4+2i) = 3(16+4) = 60$

$A$ is diagonalizable over the real numbers $\mathbb{R}$

Both (a) and (b) are true