We can express the exercise in terms of a function
[tex]n(t)=n_0\cdot e^{rt}[/tex]Where
n is the number of bacterias
t is the time
r is the relative rate of growth
From the problem we have
[tex]n(t)=10\cdot e^{0.05t}[/tex]if t=28
[tex]\begin{gathered} n(28)=10\cdot e^{0.05(28)} \\ n(28)=10\cdot e^{1.4} \\ n(28)=40.552 \end{gathered}[/tex]