Choose the true statement about global agricultural production. a. Tea and coffee are examples of non-food cash crops.
b. Cash crops contribute to primary nutrition needs.
c. Corn and wheat supply over half of the worldwide human caloric needs.
d. Subsistence crops provide food products needed for survival.

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=