How do I approach this question?

Hi I am not sure how to approach this question and would like a nudge in the right direction and the general ideas around solving it.

Two helicopters set off from Hamilton airport at time t = 0. They follow the paths

r1(t) = (140t; 140t; 5t)

r2(t) = (200t; 0; 4t)

where t is measured in hours, and distances in kilometres. After a short flight, the first helicopter encounters problems and lands immediately on Pirongia at coordinates (28; 28; 1). Three minutes later, the second helicopter alters its course to rescue the occupants of the first helicopter. It flies in a straight line towards the landing site at 250kph. How long does it take for the second helicopter to get there?