$1.$Make ABC$-$ analysis to find out what are most important items to focus.

$2.$What is your total inventory value?

$3.$What is your inventory turns ratio?

$4.$Determine safety stock level for each item based on demand:

$$Safety stock level for group A: $2$ weeks demand

$$Safety stock level for group B: $1$ months demand

$$Safety stock level for group B: $4$ months demand

$5.$Calculate inventory carrying costs of your safety stock, when:

$$Internal interest rate is $12\%$

$$Storage costs are $6\%$ of inventory value

$$Risk costs are $2\%$ of inventory value