From the Internet,  https://www.thefreedictionary.com/attractive+force


        attractive force - the force by which one object attracts another. 




Obviously, it is incorrect using this term in the problem. (Attractive force is the term from Gravitation.)

In the condition, simply OMIT this term "attractive" as IRRELEVANT.



Make a sketch or look into my lesson

    - Using vectors to solve problems in Mechanics: Force, Figures 3, 4 and 5.

in this site.



From this lesson (or from elementary consideration), the magnitude of the force under the question is

      | F | = ,


where W is the weight,   is the angle of the tunnel floor with the horizon.


We are given   = 1% = 0.01  (one percent grade).


It is so small grade that approximately  =   ( ! APPROXIMATELY, with very good precision).


Therefore,  | F | = w*0.01 = 12.4 kN * 0.01 = 12400 Newtons * 0.01 = 124 Newtons.     ANSWER