A ball travels horizontally to the left and is caught by a goalkeeper as shown in the picture. The force of the ball on the goalkeeper (\vec{F}_{BK}) results in the goalkeeper moving slightly to the left when catching the ball. If the force from the goalkeeper to the ball is expressed as \vec{F}_{KB}, which of the following is the most suitable?
a. \vec{F}_{BK} did positive work and \vec{F}_{KB} did negative work.
b. \vec{F}_{BK} did positive work and \vec{F}_{KB} did positive work.
c. \vec{F}_{BK} did negative work and \vec{F}_{KB} did positive work.
d. \vec{F}_{BK} did negative work and \vec{F}_{KB} did negative work.
e. Work from \vec{F}_{BK} or \vec{F}_{KB} can be positive or negative depending on the direction of the positive axis of the frame of reference.