if i have a 10000 $ non margin account, could i have sold 100 contracts @ the 500- 510 option call spread. what would happen for contracts being exercised before the position could be closed? with options expiring in one day, would a broker allow such a large position? if a contract was exercised, would the broke automatically exercise an option u own to offset the short? in aftermarket, when options r closed in u.s., can profits be locked in in a foreign market with an off setting put spread? what markets would be open after 4 pm eastern time u.s. and what markets recommended?