Two identical carts roll on a friction-free horizontal surface. Cart A moves due north with speed v, and Cart B moves due east with the same speed v. Which of the following best describes the direction of the total linear momentum of the two-cart system at that instant?
a) Due north
b) Northwest, 45∘ north of west
c) Northeast, 45∘ north of east
d) Northeast, 26∘ north of east