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 = 3000. 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