How are purchases worked out when proper accounting records have not been maintained?
- Asales \times $(1 - \text{margin})$ - closing inventory + opening inventory
- Bsales \times $(1 - \text{margin})$ + closing inventory - opening inventory
- Csales \times $(1 - \text{mark-up})$ - closing inventory + opening inventory
- Dsales \times $(1 - \text{mark-up})$ + closing inventory - opening inventory