Determine the asymptotic complexity of the function defined by the recurrence relation. Justify your solution using expansion/substitution and upper and/or lower bounds, when necessary. You may not use the Master Theorem as justification for your answer. Simplify and express your answer as O(n) or O(nlog n) whenever possible. If the algorithm is exponential, just give exponential lower bounds.
a) T(n) = T(n-3) + cn, T(0) = c
b) T(n) = T(n-3) + T(n-6) + T(n-7) + cnlogn, T(0) = c
c) T(n) = 2T(n/2) + c, T(1) = c