Motion maps for two objects, y and z, are shown.
object z passes object y after how many seconds?
a.) 2
b.) 3
c.) 4
d.) 5

the doppler effect is used by weather forecasters to measure 

moving clouds

the kind of relationship between atmospheric  density and altitude is inverse relationship. this means a surge in either will cut the other factor. density is mass per unit volume, it is hard to compute with only altitude 1,291 kilometers given. also, we could also use temperature and pressure to resolve density but they are not delivered.