Help asap, plz!

Well...let's see....

15310 (1.2)*1   = 18372 ....nope....that's not correct  !!!!

Let's use the points

(0, 15310)  (1,18002)  (2, 21548)  ( 3, 25642)     and this utility to generate a quadratic function :

http://keisan.casio.com/exec/system/14059932254941

We get the function

y = 350.5x^2  + 2402.7x  + 15294.7

It appears that the last answer is pretty close to this....so...."D"