Going Goats

A family of four goats had to cross a ricketty old bridge to reach greener pastures.

The bridge was heavily guarded during the day by a gang of goat-eating trolls, so the family had to attempt the crossing at night. Unfortunately, the goats had only one lantern among them, and only two goats could cross the bridge at one time.

Fat Papa Goat can cross the bridge in 8 minutes.
Slim-trim Mama Goat can cross the bridge in 5 minutes.
Baby Brother Goat can cross the bridge 10 minutes.
Sprite Sister Goat can cross the bridge in 4 minutes.

What is the fastest way for the goats to cross the bridge?

See the solution