To find out how much grain the farmer can hold we need to find the volume of the silo. The silo is made from a circular cylinder and half a sphere.
The volume of the cylinder is given by:
![V=\pi r^2h](https://img.qammunity.org/2023/formulas/mathematics/high-school/axumboiozoejyargdo4sskcbefipwsp4rb.png)
In this case r=10 and h=30, plugging this values in the equation above we have that the volume of the cylinder is:
![\begin{gathered} V=(3.14)(10)^2(30) \\ V=9420 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/ofskjquncklvd1mzqlds67bgnf247rr1bz.png)
Hence the volume of the cylinder is 9420 cubic feet.
Now we need to find the volume ot half the sphere, the volume og an sphere is given by:
![V=(4)/(3)\pi r^3](https://img.qammunity.org/2023/formulas/mathematics/high-school/zraet4fw93vx9gjz3iextthjo546ibcpwc.png)
Plugging the radius we have that:
![\begin{gathered} V=(4)/(3)(3.14)(10)^3 \\ V=4186.6 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/hgxr6eoi99cfniu1ejchrhayaokpf8szpn.png)
Now, we only need half this volume then the volume of the top of the silo is:
![V=2093.3](https://img.qammunity.org/2023/formulas/mathematics/college/pvzzcso834he2otvccox4mcibaf0xjk6sn.png)
Finally we add the volume of the cylinder and half the sphere, therefore the volume of the sylo is:
![11513.3](https://img.qammunity.org/2023/formulas/mathematics/college/sn8x15gnnt6syhursxovpsd1q7r8b5fb19.png)
and the answer is B.