$(4.)$ Knowing that at the instant shown, bar $AB$ has an angular velocity of $5ra\frac{d}{s}$ and an angular acceleration of $3ra\frac{d}{s^2},$ both clockwise, deter mine the followings by using the vector approach $($as you did in the sample problems$).(20$ points$)$

$($a$)$ angular acceleration of bar BD $(10$ points$)40$

$($b$)$ angular acceleration of bar DE $(10$ points$){}_0^{11}$