Which of the following is an example of empirical work?
a. Susanna develops a simple model to represent the life cycle of a certain species of v grasshopper.
b. Juliana collects data on frog populations in a local pond.
c. Marshal experiments with a supply and demand model, shifting the supply curve to the left and right.
d. Anaya predicts likely changes in the housing market, using a housing model.
e. Jorge builds a model city using a sophisticated computer program.