Given the points $A(5,1,0),B(-2,1,2),$ and $C(-4,5,7),$ find $($a$)$ the angle between vec$(AB)$ and vec$(AC),($b$)$ the angle between vec$(BA)$ and vec$(BC),$ and $($c$)$ the angle between vec$(CA)$ and vec$(CB).$

$($a$)\frac{?}{{?}_{B}AC}=$

$($b$)\frac{?}{{?}_{A}BC}=$

$($c$)\frac{?}{{?}_{A}CB}=$