How select the optimal pair in all combination which meet a reference value

Suppose we have data given as

for i=1:1:17520
A=d2_f(i);
B=([e1(i);e2(i);e3(i);e4(i);e5(i);e6(i);e7(i);e8(i);e9(i);e10(i);e11(i)]);
end

how we can select the optimal pair of B's which meet the value of A over every time

Thanks in advance