Speaker wire for Ba7500

your speaker is a 4 channel speaker.. it needs 3 inputs.
1 rear analog ie red/pink
1 from analog ie green
1 digital coaxial. this could be the one that has been cut-off.
can your provide a picture of the speaker?? with the wires coming out till the cut off end

is this similar to your speakers??

The Pink/Red and Green wire goes to the back of ur PC or laptop for inputs(analog)
if your PC supports digital output then u can use the digital cable the is cut-off. it will use a digital pin(black as shown in above figure)
referring to figure..
green and purple are ur inputs from computer to the woofer.
red and white cable running from the woofer to the speakers(front)
pink one in above picture is an output line to the rear speakers(you might need to use splitters to connect both rear speakers).
basically you don't need the digital output if your computer doesn't support it.