How to solve with constraints

I have

vcuaamo = 13.58823529;
sjuaamo = -4.470588235;
vcuhome = 19.125;
sjuhome = -2.111111111;
vcuaway = 8.666666667;
sjuaway = -7.125;
vculast7 = 15.57142857;
wjulast7 = 2.714285714;
vcuprepoints = 71.9;
sjuprepoints = 65.7;
a = 0.35, b = 0.25, c = 0.2, d = 0.2;
one = a+b+c+d;
one = 1;

I want to find the way this equation equals 12, by changing a, b, c, d. There are some constraints being a>b,c,d and c>b,d, and that a+b+c+d=1, also a,b,c,d > 0

12 == (vcuaamo-sjuaamo)*a+(vcuhome-sjuaway)*b+(vculast7-sjulast7)*c+(vcuprepoints-sjuprepoints)*d

[Walter Roberson]

There are an infinite number of solutions, especially once you realize that any of b, c, or d can be negative.

[Hunter Herrenkohl]

okay I also want a,b,c,d>0