Efficient Family Bridge Crossing Strategy

[mathmaniac1]

5 members of a family are to cross the bridge and the bridge can hold only 2 at a time.Its also dark so they have a lamp...They have to do the crossing in less than 30 seconds...
It takes 1 second for the boy to cross the bridge,3 seconds for his fatty brother,6 seconds for their father,8 seconds for the boys' mother and 12 seconds for their grandpa...
When two of the family are crossing together it takes the time of the slowest person to cross the bridge...(Thats obvious)
How will you get all them across?

 

[mathmaniac1]

Looks like nobody wants it.Ok,here is the answer

Spoiler

http://www.mymathforum.com/viewtopic.php?f=38&t=39218#p160599

a:1, b:3, c:6, d:8, e:12[

return trip #1: a+b, a returns : time = 4
return trip #2: d+e, b returns : time = 15
return trip #3: a+c, a returns : time = 7
final 1 way trip: a+b : time = 3

Total time = 4+15+7+3 = 29

Edit:No matter what I do I can't edit this my way...