Two masses are attached, each to either end of a spring. The spring is compressed till its potential energy is $\mathrm{U}$ and then released. Their velocity of separation at the instant the heavier mass has a momentum $\mathrm{p}$ is less than or equal to
(a) $\frac{U}{2 p}$
(b) $\frac{\mathrm{U}}{\mathrm{p}}$
(c) $\frac{2 \mathrm{U}}{\mathrm{p}}$
(d) $\frac{4 \mathrm{U}}{\mathrm{p}}$