A vacuum-propelled capsule for a high-speed tube transportation system of the future is being designed for operation between two stations $A$ and $B,$ which are $10 \mathrm{km}$ apart. If the acceleration and deceleration are to have a limiting magnitude of $0.6 g$ and if velocities are to be limited to $400 \mathrm{km} / \mathrm{h}$ determine the minimum time $t$ for the capsule to make the 10 -km trip.