Treasury Secretary Janet Yellen says it's hard to know when the federal government would run out of cash if the debt ceiling isn't raised. Bloomberg's Kailey Leinz reports. Follow Bloomberg for business news & analysis, up-to-the-minute market data, features, profiles and more: http://www.bloomberg.com Connect with us on... Twitter: https://twitter.com/business Facebook: https://www.facebook.com/bloombergbusiness/ Instagram: https://www.instagram.com/quicktake/?hl=en