Consider a small sphere $A_1$ placed inside a large spherical cavity $A_2.$ Sphere $1$ has a $D_1=6$ inch diameter, and spherical cavity $2$ has a $D_2=30$ inch diameter.

DETERMINE:

$($a$)F_{11}$

$($b$)F_{12}$

$($c$)F_{21}$

$($d$)F_{22}$