The retrieval time is around 44% (2.50 min/m3) of the total OP time. Most of this time is spent on
removing products in the front levels until the desired item comes to surface. The multiple storage depths
combined with the surface type-based storage makes retrieval the most time-consuming procedure. Note
that the initial choice of storage policies was based upon empirical criteria since, without a systematic
measurement and consideration of the real system.