Answer :
Answer: a) 138.32 and b) 35 years approx.
Step-by-step explanation:
Since we have given that
[tex]R(t)=21.4e^{0.13t}\\\\C(t)=18.6e^{0.13t}[/tex]
So, Profit is given by
[tex]Profit=R(t)-C(t)\\\\Profit=21.4e^{0.13t}-18.6e^{0.13t}\\\\Profit=e^{0.13t}(21.4-18.6)\\\\Profit=2.8e^{0.13t}[/tex]
Difference in years of 1990 and 2020=30
So, Profit becomes :
[tex]P(30)=2.8e^{0.13\times 30}\\\\P(30)=2.8\times 49.40\\\\P(30)=138.32[/tex]
(b) How long before the profit found in part (a) is predicted to double? (Round your answer to the nearest whole number.) years after 1990.
So, profit doubles , we get :
[tex]138.32\times 2=2.8e^{0.13t}\\\\276.65=2.8e^{0.13t}\\\\\dfrac{276.65}{2.8}=e^{0.13t}\\\\98.80=e^[0.13t}\\\\\ln 98.80=0.13t\\\\4.593=0.13t\\\\\dfrac{4..593}{0.13}=t\\\\35.33=t[/tex]
Hence, a) 138.32 and b) 35 years approx.