How to find the possible unknown on the given equation on GAP

Question

How to find all positive integers A and B such that

$400*A+399*B=10026475$, where $A \in [1000..5963]$ and $B \in [0..A-1]$.

I tried on this way

total:=[];; 

for A in [1000..5963] do
for B in [0..A-1] do
f:=400*A+399*B;
if f=10026475 then
Print(f);
Add(total,f);
fi;
od;od;
gap> A;
5963
gap> B;
5962 

But there are not all possible solutions of A and B.

Thanx in advance

Answer 1

Since $400\cdot 5963+399*5962=4764038\ll 10026475$ this equation has no solution as specified.