US start-up went public

[lamailo]

Could you kindly answer my tax related questions below?

Background:

2001 as Canadian citizen started employment in US with US-based start-up company
2003 was granted restricted certificate for options of company's private shares
2003 ended employment with US company; was not employed by this company again till present day

2003 moved to Canada permanently with the certificate
2007 US company went public
2010 exchanged restricted certificate for non-restricted one:
obtained "Opinion Letter" from the company
exchanged the letter and restricted certificate for non-restricted certificate from US company's broker

2010 deposited the non-restricted certificate to an account with Canadian brokerage
2010 exchanged the certificate for US company's public shares on the account
2010 sold the shares

Questions:

1. Do I owe US taxes for 2010 if I have not had any US income other than profit from stock sales mentioned above?

2. If I do, how do I calculate US and Canadian parts of my profit?
3. Do I owe Canadian taxes for 2010 on income from stock sales mentioned above?
4. If I do, how do I find a cost base?


Thanks !