Question $1$: Transportation of Hard Disk Drives

A hard disk drive $($HDD$)$ manufacturer is looking to solve a logistics problem for its North American market. The HDD manufacturer has $3$ production centres in Sunnyvale $($California$),$ Dublin $($Ireland$)$ and Bangkok $($Thailand$)$ respectively. The manufacturer serves its North American demand of HDD through $4$ warehouses in Amarillo $($Texas$),$ Teaneck $($New Jersey$),$ Chicago $($Illinois$)$ and Sioux Falls $($South Dakota$)$ respectively. The capacity of production centres, the demand served by warehouses and the transportation cost $($in USD per thousand HDDs$)$ are given in the table below. Please note, the supply from Bangkok to Teaneck is not available yet. The manufacturer wants to find how many HDDs should be supplied from each production center to each warehouse so as to minimize its transportation cost?

$\backslash$table$[[\backslash$table$[[$Transport cost$],[$USD per $1000],[$HDDs$]],$to$,$to$,$to$,\backslash$table$[[$to$],[$Capacity$],[($in $000$s$)]],],[$from Sunnyvale,$280,420,380,490,45],[$from Dublin,$1280,990,1440,1520,100],[$from Bangkok,$1510,,1600,1680,95],[$Demand $($in $000$s$),60,78,47,55,]]$

Now find the optimal solution $($obtained above$)$ by using the Stepping Stone method.

Can you please add the workng for the Stepping stone method as this is where i am stuck.