Two masters and apprentices process one kind of parts at the same time. The master (3/5) processes 21 parts in one hour, and the apprentice processes 58 parts in two hours. There are 512 parts to be processed. How many hours should they process at the same time?
师徒两人同时加工一种零件，师傅(3/5)小时加工21个，徒弟两小时加工58个，要加工512个零件，要同时加工几个小时？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">21 / (3/5)</gadget>
<output>35</output>

<gadget id="calculator">58 / 2</gadget>
<output>29</output>

<gadget id="calculator">35 + 29</gadget>
<output>64</output>

<gadget id="calculator">512 / 64</gadget>
<output>8</output>

<result>8</result>