Calculate the reorder level, minimum stock level, and maximum stock level for inventory management.

$$\text{Reorder Level} = 28,800 \text{ units}$$

The reorder level is $\boxed{\text{28,800 units}}$.

c) ii. Minimum stock level

$$\text{Normal Reorder Period} = \frac{\text{Minimum Reorder Period} + \text{Maximum Reorder Period}}{2}$$ $$\text{Normal Reorder Period} = \frac{12 \text{ days} + 24 \text{ days}}{2} = \frac{36 \text{ days}}{2} = 18 \text{ days}$$

$$\text{Minimum Stock Level} = 28,800 \text{ units} - (900 \text{ units/day} \times 18 \text{ days})$$ $$\text{Minimum Stock Level} = 28,800 \text{ units} - 16,200 \text{ units}$$

$$\text{Minimum Stock Level} = 12,600 \text{ units}$$

The minimum stock level is $\boxed{\text{12,600 units}}$.

c) iii. Maximum stock level

$$\text{Maximum Stock Level} = 28,800 \text{ units} + 32,000 \text{ units} - (800 \text{ units/day} \times 12 \text{ days})$$ $$\text{Maximum Stock Level} = 60,800 \text{ units} - 9,600 \text{ units}$$

$$\text{Maximum Stock Level} = 51,200 \text{ units}$$

The maximum stock level is $\boxed{\text{51,200 units}}$.