Concept:The pattern involves subtracting fixed values from letters and numbers in the given clusters. Explanation: From HS777 to EO377: H (8) becomes E (5) by subtracting 3; S (19) becomes O (15) by subtracting 4; 777 becomes 377 by subtracting 400. From LP987 to IL587: L (12) becomes I (9) by subtracting 3; P (16) becomes L (12) by subtracting 4; 987 becomes 587 by subtracting 400. For the missing cluster ? to KC267, reverse the operations: add 3 to K (11) to get N (14); add 4 to C (3) to get G (7); add 400 to 267 to get 667. Thus, the missing cluster is NG667.
