Closing Bell: Apple Reportedly Working on Car Software; Stocks Slide on Earnings Mix

Summary: Stocks held in the red through to the end of the day after sales warnings from Caterpillar and Under Armour spooked investors. Crude oil added to losses after closing 1%, under $50 a barrel. Sprint slumped despite a better-than-expected quarter in which its postpaid phone churn reached a record low. The telecom narrowed quarterly losses and raised its full-year operating income target. DuPont also enjoyed a positive quarter, posting adjusted earnings more than double the same period a year earlier. The chemicals company also boosted its full-year profit estimates. Apple is reportedly testing out a car operating system which could operate self-driving vehicles. Apple reportedly has dozens of engineers working on the software in Canada.