Throughput calculation in Statistical Multiplexing scenario

I found this particular homework question a bit confusing.

Q) We have two communication sessions. Host A sends unlimited data to Host A' and Host B also sends unlimited amount of data to Host B'. Two sessions go through a shared link b/w router 1 and 2. Maximum transmission rate on shared link is 1Mbps which is also the bottleneck link.Suppose this is a packet-switched network implementing statistical multiplexing on shared link. Host A generates data at a rate of 2Mbps for 20% of the time while Host B generates data at a rate of 5Mbps for 5% of the time. The rest is idle time. Calculate the average throughput of Session A-A' and B-B'.

My answer:

19% of the time when A transmits data it will get the 1Mbps transmission speed (bottleneck).. 4% of the time B will get 1Mbps speed and 1% of the time each will get 0.5Mbps speed..Considering the time when host is busy: A-A' av throughput is = (19/100 + 1/100*0.5) / 0.2 = 0.975Mbps... B-B' av throughput is = (4/100 + 1/100*0.5) / 0.05 = 0.90Mbps..

I have a feeling that the logic that I am applying is indeed correct but just wanted to confirm it..Thanks a lot!