Difficulty divided by 140 Million is approximately how many petahashes the network is.
so, 16,818,461,371 / 140,000,000 = 120 Petahash = 120,000 Terrahash.
your 1 th miner should average 1 TH.s / 120,000 TH.s (network size) X 3600 (bitcoins per day (not exact) = 0.03 BTC per day
This is about 1 bitcoin per month or $620. Your electric bill on that miner would be about $70-$100 per month.
Thanks for the refresher course
