how much kbps to expect

we have some 20 computer in network
now new net provider which is wire less internet connecttion says thier connection is 128kbps.....

so what i ideal kbps i can expect if
1)only one of the computer in network is using net....
2)if all 20 comp are using net....ie per computer what may be kbps


the net gets fast in mornings ...but at max it is upto 10kbps when i use only one comp ie internet
so is it good connection....
what is ideal download kbps that can go if i use internet in only one computer (ie internet in only one computer) and if they say they are giving 128 kbps...

actually they say 128 if i use it in one computer...i hope it should have gone more than 10kbps insn't it..?

any helps and ideas...