R(x) = revenue if x violins are produced and sold
= (price per violin in thousands of $)(number of violins)
= x(24-x)
= -x2+24x
Marginal revenue = change in revenue caused by a one unit increase in the level of production
Marginal revenue when x = 5: R(6) - R(5) = 108 - 95 = 13
If the level of production is increased from 5 violins to 6 violins, we expect that the total revenue from the sale of all 6 violins will increase by $13,000 from what the revenue was when 5 violins were produced and sold.
Do the other two parts in a similar manner.