Suppose Joey was exposed to antigen X for the first time, an…

Suppose Joey was exposed to antigen X for the first time, and 2 days later his blood serum contained 2 x 106 anti-X antibodies per milliliter. Six months later, Joey is again exposed to antigen X. 2 days after the second exposure, you would expect his serum anti-X antibody concentration to be ____________ 2 x 106 per milliliter.