During the daylight hours, a field of plants in the Midwest has a gross primary productivity value of 22\, \pu{g C/m2/day}22gC/m
2
/day22, g, C, slash, m, squared, slash, d, a, y. During the roughly 121212 hours of the night, the plants use about 6.6\, \pu{g C/m2/day}6.6gC/m
2
/day6, point, 6, g, C, slash, m, squared, slash, d, a, y.
What is the net primary productivity of this field?