Answer :
In general, the surface area of a sphere is given by the formula below
[tex]\begin{gathered} A_{sphere}=4\pi r^2 \\ r\rightarrow\text{ radius} \end{gathered}[/tex]Therefore, in our case,
[tex]\begin{gathered} r=\frac{diameter}{2}=\frac{10.4}{2}=5.2 \\ \Rightarrow r=5.2 \end{gathered}[/tex]Then,
[tex]A_{sphere}=4\pi(5.2)^2=108.16\pi[/tex]