Economics for Today 7th Edition by Irvin Tucker

تمرين 5

If a farme adds 1 pound of fertilizer per acre, the value of the resulting crops rises from $80 to $100 per acre. According to marginal analysis, the farmer should add fertilizer if it costs less than
A) $12.50 per pound.
B) $20 per pound.
C) $80 per pound.
D) $100 per pound.