If 50 apprentices can finish a job in 4 hours, and 30 journeymen can finish the same job in 5 hours, how much of the job should be completed by 10 apprentices and 15 journeymen in one hour?
Choose the correct answer.
A) 1/9 B) 29/180 C) 26/143 D) 3/20 E) 39/121
50 apprentices can finish the job in 4 hours,thus:   10 apprentices can finish the job in   4*5= 
<gadget id="calculator">  4*5</gadget>
<output>20</output>
20 hours;   In 1 hour 10 apprentices can finish 1/20 of the job.   30 journeymen can finish the same job in 4,5 hours,thus:   15 journeymen can finish the job in  5*2= 
<gadget id="calculator"> 5*2</gadget>
<output>10</output>
10 hours;   In 1 hour 15 journeymen can finish 1/10 of the job.   Therefore, in 1 hour 10 apprentices and 15 journeymen can finish 1/20+1/10=3/20 of the job.   Answer: 3/20.
<result>D</result>
If 50 apprentices can finish a job in 4 hours, and 30 journeymen can finish the same job in 5 hours, how much of the job should be completed by 10 apprentices and 15 journeymen in one hour?