A simple telephone system consists of a single toll office, two end offices each connected to the toll office with N telephones, just like the figure below. The wires between each end office and the toll office has 1 MHz capacity in each direction and each active telephone call requires 5 kHz bandwidth. 10% of the calls are long distance (calls that do not pass through the toll office are local calls, e.g. phone calls within the UCI network, while calls that do pass through the toll office are long distance calls) The busiest time of the day for calls is 9 AM to 5 PM and on average, each telephone is used to make 4 calls between 9 AM and 5 PM. The mean of call duration is 8 mins.

1. Assume that among these long distance calls, there are 80% are voice calls and 20% are video calls. The average duration for a voice call is 3 mins, and the average duration a video call is 50 mins. At a specific moment, what percentage of long distance calls are video calls?