How did Johann Bayer names stars in constellation?​

Bayer assigned a lower-case Greek letter (alpha (α), beta (β), gamma (γ), etc.) or a Latin letter (A, b, c, etc.) to each star he catalogued, combined with the Latin name of the star's parent constellation in genitive (possessive) form. The constellation name is frequently abbreviated to a standard three-letter form.

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

snell's law

refractve index = sin incidence / sin refraction