數學5識 幫忙

in the beginning of 2009,the number of mosquitoes in a city is 5000.the scientist found that after n years,there are f(n) more mosquitoes than the previous year.f(n)can be represented by the following formula:
f(n)=xn+y^n,where x and y are constants.
it is know that the numbers of mosquitoes in the beginning of 2010 and 2011 are 15004 and 35020 respectively,
(a)(i)find the values of x and y.
(ii)find the number of mosquitoes in the beginnig of 2019.
(b)a plan to kill mosquitoes will start in the beginning of 2013.the seientist expects k(m) mosquitoes can be killed in the m th year from the beginning of 2013.k(m)can be represented by the following formula: k(m)=10000(m+4)+2^(m+4) .
Sara predicts the total number of mosquitoes will keep increasing.and then she claimed that the number of mosquitoes will equel to33428364 one day in 2021.is Sara correct?explain your answer.(hint:49985000=5000x9997)