Which of the following examples does not illustrate the principle represented by the adage, "there is no such thing as a free lunch"?
a. melissa needs to pay her rent and her electric bill.
b. kevin must choose between buying a new flat screen television and buying his textbooks for this semester.
c. robert must decide between studying for his psychology exam and working at his part-time job.
d. lisa can spend her money on a new smart phone or on a weekend trip.

Wo firms, a and b, each currently dump 50 tons of chemicals into the local river. the government has decided to reduce the pollution and from now on will require a pollution permit for each ton of pollution dumped into the river. it costs firm a $100 for each ton of pollution that it eliminates before it reaches the river, and it costs firm b $50 for each ton of pollution that it eliminates before it reaches the river. the government gives each firm 20 pollution permits. government officials are not sure whether to allow the firms to buy or sell the pollution permits to each other. what is the total cost of reducing pollution if firms are not allowed to buy and sell pollution permits from each other? what is the total cost of reducing pollution if the firms are allowed to buy and sell permits from each other? a. $3,000; $1,500 b. $4,500; $3,500 c. $4,500; $4,000 d. $4,500; $2,500