Hi, bit of help needed:

A necklace has 10 beads around it. If half the beads are pink and the other half are grey, in how many ways can they be arranged so that the colours are alternate? Assume that the beads are distinguishable.

I'm stuck deciding between:

4!/2 * 4!/2 = 144

or

(4!*5!)/2 = 1440

Help?