Airplane a takes off and ascends at a rate of 3000 ft/min. at the same time, airplane b, which is flying at 30,000 ft, begins to descend at a rate of 2500 ft/min.

let h represent the height off the ground in feet, and let t represent time in minutes.

which system models this situation?

a.
h = 3000t
h = 2500 + 30,000t

b.
h = 30,000 + 3000t
h = 30,000 − 3000t

c.
h = 2500t
h = 30,000 − 3000t

d.
h = 3000t
h = 30,000 − 2500t