The total monthly revenue R(x), in dollars, generated from sales of Calculus videos is related to the amount x spent on advertising by R(x)= -8x+144x + 30x + 40 where x is in hundreds of dollars. Compute the rate of change of revenue with respect to the amount of money spent on advertising. R'(x) = Is monthly revenue increasing faster when the amount of money spent on advertising is 640 dollars or 680 dollars? O 640 dollars 680 dollars