A.
Using pythagorean theorem:
[tex]\begin{gathered} c^2=a^2+b^2 \\ where\colon \\ c=1072 \\ b=343 \\ solve_{\text{ }}for_{\text{ }}a\colon \\ (1072)^2=a^2+(343)^2 \\ a=\sqrt[]{(1072)^2-\mleft(343\mright)^2} \\ a\approx1015.645ft \end{gathered}[/tex]B.
The area will be:
[tex]\begin{gathered} A=\frac{b\cdot h}{2} \\ where\colon \\ b=343 \\ h=1015.645 \\ A=\frac{343\cdot1015.645}{2} \\ A=174183.1373ft^2 \end{gathered}[/tex]C.
[tex]174183.1373ft\times\frac{1acre}{43560ft}=3.9987ac[/tex]