Consider the relations R(A, B), S(B,C), and T(C, D). Assume that R, S, and T are stored in B(R), B(S), and B(T) blocks, respectively. Furthermore, assume that you have a buffer of (approximate) size M 

Assuming that you use the block nested-loop join algorithm to implement natural join operations, specify the time complexity to evaluate the relational algebra expression (????⋈????)⋈????. You can make the assumption that ????(????⋈????)≤ ????2, where ????(????⋈????) is the number of blocks to store (????⋈????)