Final answer:
The function k(t) = 280(.88)^t represents decay, A0 is the initial amount of the loan, and r is the percent change that represents the rate at which the loan decreases over time.
Step-by-step explanation:
1) Identify k(t) as growth or decay: The function k(t) = 280(.88)^t represents decay because the value of (.88)^t is less than 1, and as t increases, the value of k(t) decreases continuously.
2) Name A0, starting amount: A0 represents the initial amount or starting amount of the loan. In this case, A0 is the $280 that Kira initially owes to her grandmothers.
3) Find r, the percent change: The value of r can be found by taking the natural logarithm (ln) of (1 + p), where p is the growth rate. In this case, r = ln(0.88), which is approximately -0.1283. The percent change represented by r is the rate at which the loan decreases over time.