Following are the steps to be followed while solving this query:
Step 1) Take the x, y and z components of the position and momentum of the particle. Note since, the particle is in xy plane, z components will be zero.
Step 2) Consider the formula for angular momentum. It is . Write this in terms of a 3×3 matrix.
Step 3) Solve the matrix. You should obtain
Step 4) Substitute the values. They are x = vt, y = b, px = mv and py = 0 to obtain