We have been given gross domestic product (in billions of dollars) can be approximated by [tex]P(t)=564+t(36t^{0.6}-101)[/tex].
(a) In this part, we need to compute the derivative of this function:
[tex]P'(t)=\frac{d}{dt}(564+t(36t^{0.6}-103))\\P'(t)=\frac{d}{dt}(564)+\frac{d}{dt}(t(36t^{0.6}-103))\\P'(t)=0+57.6t^{0.6}-103\\[/tex]
[tex]P'(t)=57.6t^{0.6}-103[/tex]
(b) In this part, we need to find the value of P'(45). So, we will substitute t=45
[tex]P'(45)=57.6(45)^{0.6}-103\\P'(45)=565.3924-103\\P'(45)=462.39[/tex] Billion dollars per year.
(c) P'(45)=462.39 represents that 45 years after 1960, that is, in 2005, the GCP was changing at a rate of 462.39 billion dollars per year.