(Source: The Motley Fool Canada) BlackBerry Ltd. (TSX:BB)(NYSE:BB) stock has dropped 15.9% as of close on April 4 since releasing its fiscal 2018 fourth-quarter and full-year results on March 28. This dramatic plunge sent the stock into negative territory for 2018 before the first trading week in April came to a close. However, shares are still up 24% year …