What is it for 15 years?

Which statement about the graph of y = 8(0.25)^2

Mexico city, mexico, is the world's second largest metropolis and is also one of its fastest-growing cities with a projected growth rate of 3.2% per year. its population in 1991 was 20,899,000 people. use the formula p = 20.899e0.032t to predict its population p in millions with t equal to the number of years after 1991. what is the predicted population to the nearest thousand of mexico city for the year 2010?

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.