Let $u=($:$7,-4$:$)$ and $v=($:$-4,5$:$).$ Find the $(a)$ component form and $($b$)$ magnitude $($length$)$ of the vector.

$\frac{5}{13}u+\frac{12}{13}v$

a$.\frac{5}{13}u+\frac{12}{13}v=$

$($Type integers or simplified fractions.$)$