I'm not sure but it would solve like first put 200 in place of n and through formula we'll get 250 then next time put 400 in place of n and solve from that formula and we'll get 500. So, overall answer will come 250/500.
200+200/4=250
400+400/4=500
250/500
this we called 'biomathematics'
Don't solve by putting overall value in place of n i.e 200/400 solve separately