A circular plasmid of 10,000 base pairs (bp) is digested with two restriction enzymes, A and B, to produce a 3000 bp and a 2000 bp bands when visualised on an agarose gel. when digested with one enzyme at a time,only one band is visible at 5000 bp. If the first site for enzyme A(A1) is present at the 100th base, the order in which the remaining sites (A2,B1 and B2) are present is?