68. The initial position vector
r
o
satisfies
− r
= ∆
r, which results in
=
− ∆r = (3ˆj− 4 ˆk) − (2ˆi− 3ˆj+ 6 ˆk) = −2.0ˆi+ 6.0ˆj− 10 ˆk
where the understood unit is meters.