Given
The total revenue in dollars from the sale of a toasters is:

The marginal revenue R'(x) is the first derivative of the total revenue

(a) R'(100)
The value of the marginal revenue at 100 can be obtained by substitution:

Answer: 20
(b) R'(450)
The value of the marginal revenue at 450 is obtained by substitutionubstit

Answer: -330