Convert kibibit per second to hour per gigabyte

Internet connections are sold in megabits per second (Mbit/s or Mbps) but downloads are shown in megabytes per second (MB/s), and there are 8 bits in a byte: a 100 Mbit/s line moves at most 12.5 MB/s, and a gigabit line 125 MB/s. In practice protocol overhead takes 5–10 % off that. So a 5 GB game download on 100 Mbit/s takes about 7 minutes at best, not 50 seconds. Lower-case b is bits, capital B is bytes.