Final answer:
The slope of a budget line represents the opportunity cost of the good on the horizontal axis. It is usually negative, reflecting the need to give up some of one good to obtain more of another. The slope is found by the ratio of the prices of the two goods being compared.
Step-by-step explanation:
The slope of a budget line in an economic context represents the opportunity cost of the good on the horizontal axis. Here, if we are trading coconuts for fish with Friday, the slope will indicate how many fish need to be given up to get one more coconut, or vice versa. The options presented suggest the slope could be negative or positive; however, in the context of budget constraints, the slope is usually negative because you give up some quantity of one good to gain more of another. The exact slope can be determined by the ratio of the prices of the two goods.
Using Alphonso's example as a reference, where the slope is -0.25, it implies that for every unit of good on the horizontal axis he wants to purchase, he must give up 1/4 of a unit of the good on the vertical axis. In this example, for every four bus tickets, one burger is given up. The slope is negative, reflecting the trade-off between two goods. To apply this to the student's original question, you would need the specific ratio of how many coconuts can be traded for fish, which would give the slope of the budget line for trading with Friday.