The constraint for the potential plant site 2 can be written as:
a. x21 + x22 + x23 less or equal than 2100y2
b. x21 + x22 + x23 greater or equal than 2100y2.
c. x21 + x22 + x23 less or equal than 2800 y2.
d. x21 + x22 + x23 greater or equal than 2800y2.
e. none of the above.