The graph below represents the potential energy `U` as a function of position r for a particle of mass `m`. If the particle is released from rest at position `r_0`, what will its speed be at position `3r_0` ?
Options:
(a) `sqrt((3uuu_0)/m)`
(b) `sqrt((4uuu_0)/m)`
(c) `sqrt((2uuu_0)/m)`
(d) `sqrt((6uuu_0)/m)`