An intergalactic cruiser has two types of guns: a photon cannon that fires a beam of laser light and an ion gun that shoots ions at a velocity of 0.910c relative to the cruiser. The cruiser closes in on an alien spacecraft at a velocity of 0.780c relative to this spacecraft. The captain fires both types of guns.
Find at what speed do the aliens see
(a) the laser light and
(b) the ions approach them?
Find at what velocity do the aliens see
(c) the laser light and
(d) the ions move away from the cruiser?