In the following image, regarding a CD shop that rents its music CDs.
My question is regarding the correct multiplicity of X. I can think of several possibilities for X:
- X= 1..1 as each copy of CD can rented by one member only at one time. All copies are assumed to be rented at some point.
- X= 0..1 as each copy of CD may be rented by one member only at one time. Perhaps some CDs are never rented out.
- X= 0..N as each copy of CD may be rented to any member during CD's lifetime at the shop (but it should not be at the same time)
Could you please clarify this point for me?