Snap Inc.’s stock (SNAP.N) closed at $21.44 a share Tuesday. Snap originally priced its initial public offering at $17 a share but the stock opened on March 2 at $24 a share. It reached a peak of $29.44 on Friday. There are concerns about the future of Snap’s growth as well as its profitability. Institutional traders are paying between 15 and 40 % annualized interest to borrow shares to sell short, expecting a steep decline in the price of the stock.