During a physical exercise drill, athletes have to run to the first marked line then back to the starting point. They then turn around and run to the next marked line and then back again to the starting point. This repeats until the athlete reaches the final marked line. The distance in feet run for each line can be represented by the function D(l)=2(20l) where l is the number of lines the athlete ran to and from. How many feet would an athlete have run in total if he had just finished running to and from the 10th line? : feet