Hogwarts

A group of soon-to-be-first-years at Hogwarts School of Witchcraft and Wizardry just walked into the Great Hall. Everybody has been sorted into a house of either Slytherin, Hufflepuff, Gryffindor, or Ravenclaw. Hufflepuff = Loyal and Trustworthy; Ravenclaw = cunning and intelligent; Gryffindor = brave and noble; Slytherin = keen and ambitious.
There are still 4 kids to be sorted. Their names are Billy, Shelby, Anthony, and Kristen. The sorting hat takes some time for each kid. Find out the amount of time the hat took and which house each kid ended up in.

Clue 1. Shelby is VERY smart.

Clue 2. Billy is a scaredy cat.

Clue 3. Billy and the boy in Slytherin took under a minute to be sorted.

Clue 4. Billy always keeps promises and is not very bright.

Clue 5. The person in Gryffindor took the longest.

Clue 6. Anthony was the fastest to be sorted.

Clue 7. Billy was sorted 30 seconds faster than the Ravenclaw.