It can be done in 2 ways.


First way is to sum two geometric progressions, using standard formulas.


    First GP starts with 5600 (Jan) and has 9 following terms from 2 to 10 (Feb-Oct) inclusive, 
    that diminish with the common ratio of 0.98.

    Then this term    (Oct)  is the first term of the other, growing GP with the common ratio of 1.04.

    This second sequence continues to the 25-th term   inclusive, which corresponds to the last Jan.


          (It is how I understand the problem's description, although it is in fog in this part).


It is really boring way.


Another way is to do it in several clicks with Excel.


I did it in this way and got the ANSWER  148449.09.    ANSWER


Notice that I rounded at the very end and did not round on the way.