Two dogs pull horizontally on ropes attached to a post; the angle between the ropes is $60.0^{\circ} .$ If $\operatorname{dog} A$ exerts a force of 270 $\mathrm{N}$ and dog $B$ exerts a force of $300 \mathrm{N},$ find the magnitude of the resultant force and the angle it makes with dog $A$ 's rope.