If vectors $\mathbf{A}$ and $\mathbf{B}$ are given by $\mathbf{A}=5 \hat{\mathbf{i}}+6 \hat{\mathbf{j}}+3 \mathbf{k}$ and $\mathbf{B}=6 \hat{\mathbf{i}}-2 \hat{\mathbf{j}}-6 \hat{\mathbf{k}}$. Which is/are of the following correct?
(a) A and B are mutually perpendicular
(b) Product of $A \times B$ is the same $B \times A$
(c) The magnitude of $\mathrm{A}$ and $\mathrm{B}$ are equal
(d) The magnitude of $A \cdot B$ is zero