We have the function
[tex]S(t)=1200+540\ln(31t+e)[/tex]
And we want to evaluate S(13), therefore
[tex]\begin{gathered} S(13)=1200+540\ln(31\cdot13+e) \\ \\ S(13)=1200+540\operatorname{\ln}(403+e) \\ \\ \end{gathered}[/tex]
Here we must use a calculator to get the result
[tex]\begin{gathered} S(13)=1200+540\operatorname{\ln}(403+e) \\ \\ S(13)=1200+540\cdot6.00566 \\ \\ S(13)=1200+3243.05587 \\ \\ S(13)=4443.05587708 \\ \\ S(13)=4443 \end{gathered}[/tex]
The predicted sales in 13 years are 4443 computers