Zhou Yong and Wang Nan went to school from home at the same time. The distance between their home and school was 1600 meters. Zhou Yong arrived 5 minutes earlier than Wang Nan. At this time, Wang Nan was still 400 meters away from school. How many minutes would it take Zhou Yong to complete the journey?
周勇和王南同时从家去学校，他们家到学校的距离是1600米，周勇比王南早到5分，这时王南离学校还有400米，周勇行完全程需多少分？
<gadget id="calculator">400 / 5</gadget>
<output>80</output>

<gadget id="calculator">1_600 / 80</gadget>
<output>20</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<result>15</result>