1. Find \(\overrightarrow{PQ}\) for a general point Q on l, e.g., \(-3\mathbf{i} + 6\mathbf{k} + \mu(2\mathbf{i} - \mathbf{j} - 2\mathbf{k})\).

2. Calculate the scalar product of \(\overrightarrow{PQ}\) and a direction vector for l and equate the result to zero.

3. Solve for \(\mu\) and obtain \(\mu = 2\).

4. Carry out a complete method for finding the length of \(\overrightarrow{PQ}\).

5. Obtain answer 3.