We find that the following function is the one described by the problem:
[tex]P=kt[/tex]Now, we replace the values given to determine the value of k:
[tex]87.75=k(13)\Rightarrow k=\frac{27}{4}[/tex]Finally, the expression that accurately describes the problem is:
[tex]P=\frac{27}{4}t[/tex]