Figure $1$ SCARA Robotic Arm

a$)$ If $$ dot ${?}_1=10ra\frac{d}{s}$ and $l_l=2\mathrm{.}5$ feet, what is the absolute velocity of joint $B_1?$

b$)$ If $$ dot ${?}_2=15ra\frac{d}{s}$ with respect to link $l_1$ and $l_2=1\mathrm{.}5$ feet, what is the relative velocity of joint $B_2$ with respect to joint $B_1?$

c$)$ What is the angular range $$ of link $l_l$ as given in the problem statement?