Antibodies identify and neutralize foreign objects inside the body. Humans and other vertebrates have an immune system that uses antibodies to fight bacteria, viruses, toxins, and other foreign objects. Antibodies are complex, Y-shaped protein molecules that develop from plasma cells, which in turn develop from "B lymphocytes" produced by the bone marrow. The plasma cells can generate a very large array of different antibodies, each of which can combine with and destroy an antigen (foreign molecule). Antibodies react to very specific characteristics of different antigens, binding them to the top ends of their Y-shaped form.
Once the antibody and antigen combine, the antibodies deactivate the antigen or lead it tomacrophages(a type of white blood cell) that ingest and destroy it. High counts of a particular antibody may persist for months after an invasion before eventually diminishing. However, the B cells can quickly manufacture more of the same antibody if exposure to that particular antigen reoccurs. Vaccines work by "training" B cells to recognize and react quickly to potential disease molecules.

The main idea of the paragraph is that an energy audit should be done as a first step toward saving energy dollars. The details that follow are some of the items an audit concentrates on. The question, however, asks you to identify what precedes, or comes before, the installation of an energy-saving device.

A 120-volt circuit has a resistance of 12 ohms. A current of 10 amperes is flowing through the circuit (120 volts divided by 12 ohms = 10 amps).

Five years contain 60 months, so multiply $450 (monthly payment) 60 = $27,000 (total payments). Then add $27,000 (total payments) + $2,000 (down payment) = $29,000 (total cost).