Why would it be easier to measure the characteristics of intrinsically less luminous cepheids than more luminous ones?

An object starts from rest at point f and speeds up continuously as it moves around an oval. a. choose a point about 1/8 th of the way around the oval from point f, and label it point g. draw a vector to represent the velocity of the object at point g. b. determine the change in velocity vector   between points f and g.

If angle "a" is 25°, angle "b" is: a) equal to angle c b) less than angle c c) greater than angle c

It is really hard for me right know