How far do the two cars travel in this time?

135kph = (135,000/3600s) = 37.5m/sec.
150kph = (150,000/3600s) = 41.667m/sec.

Distance the police car takes to reach speed = 1/2(vt), = 1/2(41.667 x 7.8), = 162.5 metres.
In 7.8s., the speeder will have travelled (7.8 x 37.5) = 292.5 metres.
Distance between police car and speeder = (292.5 - 162.5) = 130 metres.
Closing rate = (41.667 - 37.5) = 4.167m/sec.
1) Time to catch up = 7.8 + (130/4.167), = 39 secs.
2) (39 x 37.5m/sec) = 1,462.5 metres (1.4625km.).