(1)→L=−mv√2RˆkWhen the particle is moving from A to B(2)→L=mv[R√2a]ˆkWhen the particle is moving from C to D(3)→L=mv[R√2a]ˆkWhen the particle is moving from B to C(4)→L=mv√2RˆkWhen the particle is moving from D to A