Communication with vendors & BD , sending defective products back to the vendor, Quality Control - of the issues, learned to manage and clear issues in given time, how to manage the break even point or profit , without any loss for the company, co-workers has always been supportive and helping, hardest part of the job? - well I don't believe there is anything hard when you give your 100% , most enjoyable part of the job - is giving your 100% and then rejects are shipped without any loop hole.