Suppose, in the North, One Unit of Labor Produces $f _ { n }$

Suppose, in the North, one unit of labor produces $f _ { n }$ units of fish or $c _ { n }$
Units of chips. In the South, one unit of labor produces $f _ { s }$
Units of fish and $c _ { s }$
Units of chips. For the South to specialize in fish, which of the following must be true?

A) $f _ { s } > c _ { s }$
B) $\left( f _ { s } / c _ { s } \right) > \left( f _ { n } / c _ { n } \right)$
C) $\left( c _ { s } / f _ { s } \right) < \left( c _ { n } / f _ { n } \right)$
D) $\left( f _ { s } / c _ { s } \right) < \left( f _ { n } / c _ { n } \right)$
E) $f _ { s } \cdot c _ { s } < f _ { n } \cdot c _ { n }$