Tesla unveiled more affordable versions of its best-selling Model Y SUV and its Model 3 sedan on Tuesday at $39,990 and $36,990 , respectively, as the electric-vehicle maker seeks to reverse falling sales and waning market share amid rising competition . Tesla shares fell 2.1% in afternoon trading. Chief Executive Elon Musk has for years promised mass-market vehicles, though last year he canceled plans to build an all-new $25,000 EV, Reuters first reported. Late last year, Musk said the vehicle