Assume That the Real Output of a Developing Nation Increases

Assume that the real output of a developing nation increases from $50 billion to $62 billion, while its population expands from 100 to 115 million. As a result, real income per capita has increased by about

A) $39 per person.
B) $64 per person.
C) $12 per person.
D) $27 per person.