Don't understand please help

Bryce, a mouse lover, keeps his four pet mice in a roomy cage, where they spend much of their spare time, when they're not sleeping or eating, joyfully scampering about on the cage's floor. Bryce tracks his mice's health diligently and just now recorded their masses as 0.0207 kg, 0.0101 kg, 0.0227 kg, and 0.0115 kg. At this very instant, the x- and y-components of the mice's velocities are, respectively, (0.521 m/s, -0.479 m/s), (-0.849 m/s, -0.835 m/s), (0.191 m/s, 0.805 m/s), and (-0.309 m/s, 0.745 m/s). Calculate the x- and y-components of Bryce's mice's total momentum, px and py. Px = kg.m/s Py = kg.m/s