Answer:
Practical domain: 
 
Roger can earn $510 at most when every member of the audience purchases a video 
Explanation:
The function 
 
Gives us Roger's earnings when he sells v videos. Knowing the play’s audience consists of 230 people and also each one buys no more than one video, v can take values from 0 to 230 or. equivalently 
 
Those limits become the practical domain of E(v) because if we chose v outside of it, the function would lose validity 
If nobody is willing to purchase a video, v=0 and Roger's earings would be 
 
If every person from the audience purchases a video, then v=230 because each person can only purchase 1 video 
In that case, where v=230, then 
 
Roger can earn $510 at most.