XYZ company currently uses a Gigabit Ethernet (1000mbits/sec) link to do nightly backups between 2 sites.
In January, they backup 1,000GBytes/night.
This number grows by 100GBytes each month. (For simplicity, assume a step-change at the end of each month).
Their backup-window is 1am-to-4am each night.
The cost of a GigE link is $1000/month.
The cost of a faster OC-48 (2.488Gbits/sec) link is $2000/month.
Assume the full 1.0Gbits/sec and 2.488Gbits/sec is available
for backup-data-payload on each link (i.e. ignore POS/framing overheads, and links are always "filled" with data)
Including January, and for the period January-December:
a. Which months can they use the GigE link; when must they change to the OC-48 link?
b. What is their total link-cost for the 12-month period?