Select all situations that can be modeled with a linear function. A taxi charges an initial fee of $2.00 and $1.50 for each additional mile. Apopulation in a town decreases by 15% each year. An airplane flying at an altitude 33,000 feet descends at a rate 20 feet per minute. A pizza restaraunt charges $5.50 per pizza, and $0.50for each additional topping. A cell phone doubles in time every two years