Bisi and Co$.$ has the following details about its stocks:

$\backslash$table$[[$Maximum usage,$20,000$ units$],[$Maximum re$-$order period,$3$ months$],[$Minimum usage $,10,000$ units,$],[$Minimum re$-$order period,$1$ month$],[$Normal usage,$15,000$ units$],[$Normal re$-$order period,$2$ months$],[$Re$-$order quantity,$30,000$ units$]]$

You are required to calculate the;

i$.$ Re$-$order level

ii$.$ Maximum stock level

iii. Minimum stock level

iv$.$ Average stock level