US STOCKS-Wall St set to extend selloff
* Amazon jumps after posting unexpected profit
* Visa rises after results beat expectations
* Biogen slumps after slashing forecast
* Futures: Dow down 31 pts, S&P down 2 pts, Nasdaq up 3 pts (Adds details, comment, updates prices)
By Tanya Agrawal
July 24 (Reuters) - Wall Street was set to open slightly lower on Friday with major indexes poised to end the week lower amid a mixed bag of earnings from big companies and the downward spiral of commodity prices.
Amazon.com shares jumped 21.5 percent to $585.64 in premarket trading, a day after the online retailer posted an unexpected quarterly profit.
Dow component Visa was up 6.3 percent at $76.29 after the credit and debit card company's results handsomely beat expectations.
Starbucks rose 4.8 percent to $59.26 after the world's biggest coffee chain reported a higher quarterly profit. Continuación...