For larger input size:

• D(n) = time to divide n input elements into subproblems, each of size n/b
• C(n) = time to combine solutions to subproblems

Thus we generate the recurrence:

$$T(n) = \left\{ \begin{array}{ll} \Theta(1) & {\rm if} \; n \... ... a T(n/b) + D(n) + C(n) & {\rm otherwise} \end{array} \right.$$