editing uptime output with sed?

[lbland]

hi-

sorry for the generic question...

how do I take uptime output:
  1:45PM  up 6 days,  3:58, 11 users, load averages: 0.30, 0.24, 0.21
and get the 2nd to last value with sed? (how do I get sed to output 
0.24 to stdout)?

TIA-

-lance