In order to calculate the number of protozoa after 4 hours, let's use t = 4 in the function p(t) and then calculate its value:
[tex]\begin{gathered} p(t)=0.02t^4+0.3t^3+7t^2 \\ p(4)=0.02\cdot4^4+0.3\cdot4^3+7\cdot4^2 \\ p(4)=0.02\cdot256+0.3\cdot64+7\cdot16 \\ p(4)=5.12+19.2+112 \\ p(4)=136.32 \end{gathered}[/tex]Rounding to the nearest whole number, the answer is 136 protozoa.
