I've been taking a french class and I have been learning about etre. However, one thing I don't know how to do is conjugate etre when it follows two...

I've been taking a french class and I have been learning about etre.  However, one thing I don't know how to do is conjugate etre when it follows two names such as in the example: Sophie et Alice ___ amies.  Could someone help me with how to conjugate it for this because it doesn't fit any other conjugations.