We have the following function
![D(t)=2.5\sin(\pi t)/(6)+12](https://img.qammunity.org/2023/formulas/mathematics/college/cx6hnatqhcvwu92ga33cyhj8ua3irsscpg.png)
The maximum and minimum of that function happens when sin(x) = 1 or sin(x) = -1, respectively.
Then let's find the maximum, that happens when the sin value is 1
![\begin{gathered} \begin{equation*} D(t)=2.5\sin(\pi t)/(6)+12 \end{equation*} \\ \\ D(t)=2.5\cdot1+12 \\ \\ D(t)=2.5+12 \\ \\ D(t)=14.5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/g46vgdk0cbb9zafzga9ptruj2miecjvvn4.png)
And the minimum, when sin value is -1
![\begin{gathered} \begin{equation*} D(t)=2.5\sin(\pi t)/(6)+12 \end{equation*} \\ \\ D(t)=2.5\cdot(-1)+12 \\ \\ D(t)=-2.5+12 \\ \\ D(t)=9.5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/gb2wucm0hfvxv3eaxhz0efup171j0oz8cy.png)
Then the least: 9.5 hours; greatest: 14.5 hours.