I'm very confused on these questions, if someone could that would be greatly appreciated.

a. if ab is 20 and bc is 21, based only on the appearance of the figure, what is a good estimate for the length of ac? how do you know?

b. if the actual length of ac is exactly what you computed in part a above, what is the measure of angle abc? how do you know?

c. given the information from a and b above, if ae is 10 and a. f is half of ac, what is the special name for segment ef as it relates to triangle abc?

d. given the result from c above, if the measure of angle efb is 43.6°, what is the measure of angle fbc? how do you know?

e. if triangle dcb is congruent to triangle abc, what kind of shape is abcd? how do you know?