You Are in a Spaceship Traveling Away from Earth $+x$ Direction Is the Direction in Which Your Ship Is Traveling

You are in a spaceship traveling away from earth. You and Mission Control on earth agree that the $+x$ direction is the direction in which your ship is traveling relative to the earth. If you choose your own frame to be the Home Frame (so that the earth is the Other Frame) , what is the sign of $\beta$ , according to the convention established in this chapter?

A) Positive
B) Negative
C) We are free to choose $\beta$ to have either sign.