Congcong used the self-study class time to do Chinese and math homework. He used (1/5) of the self-study class time for Chinese and (1/4) of the self-study class time for math. A self-study class is 40 minutes. After Congcong finishes his Chinese and math homework, how long is left for the self-study class?
聪聪利用自习课时间做语文和数学作业，他做语文用了自习课时间的(1/5)，做数学用了自习课时间的(1/4)．一节自习课40分钟，聪聪做完语文和数学作业后，自习课还剩多长时间？
<result>20</result>