Three processes A, B and C are admitted into the ready queue by the long-term scheduler. The processes are admitted -- first process C, then B, and then A -- without any delay between the admissions. The short-term scheduler uses a Round-Robin scheduling policy to assign processes to run on the CPU. The time quantum is 4ns. The CPU burst times are 48ns, 72ns and 92ns, for  A, B and C respectively. Assume that the processes make no I/O requests and all of them successfully complete. You may also assume that no other processes or OS activity are important for your computations. 

Based only on the information given, what is the average turnaround time (in ns) for these 3 processes? Give your answer to 2 decimal places.