A spacecraft with a mass of 3000 kg is moving in the positive x-direction with a velocity of 200 m/s through the empty expanse of space, where the gravitational forces can be neglected. The spacecraft ignites its engines, and the thrust force varies with time as shown in the figure below. It is assumed that the mass lost by the spacecraft during the burn time is negligible. 

Determine the following:

i) What is the maximum speed attained by the spacecraft during the burn period?

ii) At what time during the burn does the spacecraft achieve its maximum speed.