For each of the following, perform the indicated computation.

(a) $(-6\,\mathit{\vec i}+2\,\mathit{\vec j}-7\,\mathit{\vec k}) - (6\,\mathit{\vec i}+10\,\mathit{\vec j}+\,\mathit{\vec k}) =$

(b) $(-6\,\mathit{\vec i}+5\,\mathit{\vec j}-2\,\mathit{\vec k}) - 4(2\,\mathit{\vec i}-2\,\mathit{\vec j}+5\,\mathit{\vec k}) =$