To find volume $ V $ use formula:
$$ V = \dfrac{ 4 \cdot r^3 \cdot \pi}{ 3 } $$After substituting $r = 12.5\, \text{in}$ we have:
$$ V = \dfrac{ 4 \cdot \left( 12.5\, \text{in} \right)^{3} \cdot \pi}{ 3 } $$ $$ V = \dfrac{ 4 \cdot 1953.125\, \text{in}^3 \cdot \pi}{ 3 }$$ $$ V = \dfrac{ 7812.5\, \text{in}^3 \cdot \pi}{ 3 }$$ $$ V = 2604.1667\, \text{in}^3 \cdot \pi $$