Koo Mensah use two types of raw material, 'Sibi' and 'Woma' as components. Details of the materials are as follows:

Maximum Consumption : $600$ Units per week

Minimum Consumption : $200$ Units per week

Re$-$order quantity : Sibi $900$ Units and Woma $950$ Units

Re$-$order period: Sibi $3$ to $5$ weeks Woma $4$ to $6$ weeks

Required: Calculate: $($a$)$ Minimum stock level,

$($b$)$ Maximum stock level,

$($c$)$ Average stock level,

$($d$)$ Re$-$order level.