Answer:
The time taken is 4.79 minutes.
Step-by-step explanation:
[tex]P = Po(1.4)^{t}[/tex]
initial Population, Po = 400
Final population, P = 2000
Let the time is t.
[tex]2000 = 400(1.4)^{t} \\5 = (1.4)^t\\log 5 = t log 1.4\\0.6989 = 0.146 t \\t = 4.79 minutes[/tex]