Point $A$ is on the ground, and points $B$ and $C$ are $h=20m$ above

the ground. Point $B$ is directly above point $A,$ and point $C$ is $L=60m$

away from point $A$ as shown.

a$)$ How much work must be done by an external

agent to move a $3kg$ object from rest at point $A$ to

rest at point $B?$

b$)$ How much

object from rest at point $A$ to rest at point $C?$