Final answer:
Without explicit information on the spending patterns of persons A and B over the time periods mentioned, we cannot determine the correct answer. The provided references discuss economic concepts such as costs and supply and demand but do not relate to individual spending rates.
Step-by-step explanation:
From the information provided, we can deduce person A's and person B's spending behavior over two time periods, from time 0 to l1 and from l1 to l2. We need to analyze the hints to fit the correct descriptions of the rates at which A and B spend money.
Looking at the options provided:
- (a) Person A spends money at a constant rate, which means the spending neither increases nor decreases with time; it's a fixed amount per time interval. Person B spends money at an increasing rate, starting at some initial value and then spending more as time goes on.
- (b) Person A spends at a decreasing rate, indicating a start with a certain spending rate that declines over time until it might reach zero. Person B spends at a constant rate, maintaining the same spending as time progresses.
- (c) For Person A, the rate is increasing starting from a positive value and getting higher. For Person B, the rate is constant which indicates a steady rate of spending over time.
- (d) Both Person A and Person B are spending at a constant rate, indicative of a fixed rate of expenditure that does not change over time.
Using the references, we can see that they pertain to the concepts of costs and supply and demand in economics. Unfortunately, the references provided do not directly answer the question about the rates of spending for two individuals over specified time periods. Therefore, to answer the question correctly, we would require additional context or information describing the spending patterns of persons A and B over the time intervals mentioned.