John Student has just bought 250 shares in a hi-tech stock that is currently valued at $60 per share. Financial analysis indicates that the expected return on the stock is 15% and the volatility is 12%. The return is known to be lognormally distributed. Assuming that the return and volatility remain stable for the next three years, find the probability that Johns investment will be worth at least $18,000 in 3 years time.