$\epsilon$ Day Problem 1

Krish just learnt about the works of Michael Faraday and got amazed to learn them.

He tried to do an experiment for the same at his home. He took a coil with 12 loops and surface area of 20 ${m}^{2}$ . He also noticed that the magnetic field strength is in the form [ ${t}^{2}$ + 56789], where t is the time the magnet was inside the coil. He wonders for what minimum time he has to keep it inside the coil so that $\epsilon$ is maximum?

Note: Krish has now generated a love for the 1000th decimal place but surely not beyond it!