In order to better differentiate its product from generic brands, the cereal company first hired a marketing firm that specializes in creating campaigns to build brand awareness and then retools its factory to produce a variety of different shapes of cereal.

(A) then retools its factory to produce a variety of different shapes of cereal
(B) retools its factory to produce a variety of different shapes of cereal
(C) then retooled its factory to produce a variety of different shapes of cereal
(D) then will retool its factory to produce a variety of different shapes of cereal
(E) then produces a variety of different shapes of cereal through retooling its factory