Math help...ahhh!?

Tricky math question?


the four numbers a %26lt; b %26lt; c %26lt;d can be paired in six different ways. If each pair has a different sum, and if the fourt smallest sums are 1, 2, 3, and 4, what are all the possible values of d?

Math help...ahhh!?
d = 4





a=0


b=1


c=2


d=4





Six pairs are: ab,ac,ad,bc,bd,cd


ab=01: 0+1=1


ac=02: 0+2=2


ad=04: 0+4=4


bc=12: 1+2=3


bd=14: 1+4=5


cd=24: 2+4=6


all sums are different and the four smallest sums are 1,2,3,4