I am having a hard time applying Little's Law to two subsystems.

A system is comprised of 100 smaller systems. 50 of these have a customer arrival rate of 10 per second and a expected delay time of 5 seconds. The other 50 have a customer arrival rate of 20 per second and an expected queue lengths of 1. Compute the expected delay time for the system as a whole.

I found out the queue length for the first one and got 50. I also figured out the wait time for the second with .05. I am unsure of how to get the delay time for the complete system. Is it just an average of the two subsystems?

Thank you for any help.