6. (3 points) Person A and Person B work together to process a batch of parts, which can be completed in 8 hours. If Person A works alone, it would take 12 hours to complete the task. Now, Person A and Person B work together for $2 \frac{2}{5}$ hours, after which Person A is reassigned to other work, and Person B continues to produce 420 parts to complete the task. How many parts did Person B process in total?
【Solution】Solution: The total number of processed parts is:
$$
\begin{array}{l}
420 \div\left(1-2 \frac{2}{5} \times \frac{1}{8}\right) \\
=420 \div\left(1-\frac{3}{10}\right) \\
=420 \div \frac{7}{10} \\
=600 \text { (pieces); }
\end{array}
$$

The total number of parts processed by person B is:
$$
\begin{array}{l}
600-600 \div 12 \times 2 \frac{2}{5} \\
=600-120 \\
=480 \text { (pieces); }
\end{array}
$$

Answer: Person B processed a total of 480 parts.