The algorithm to map data areas given in Section 7.9 requires that we verify that low for the leader of A's equivalence set does not cause the space for the equivalence set of A to extend before the beginning of the COMMON block and that we calculate high for the leader of A to increase the upper limit of the COMMON Mock, if necessary. Give for mulas in terms of next. the offset of A in the COMMON block, and last, the current last word of the block. '0 make the lest and to update last if necessary .