if u have a concave mirror whose focal length is 100cm and you want an image that is upright and 10 times as tall as the object, where should you place the object?

The two stars in a certain binary star system move in circular orbits. the first star, alpha, has an orbital speed of 36 km/s. the second star, beta, has an orbital speed of 12 km/s. the orbital period is 137 d. a) what is the mass of the star alpha? b) what is the mass of the star beta?