John is packing his belongings to be moved into his dorm room. He is almost finished and notices that he has two partially filled boxes left. One box is $\frac { 3 }{ 4 } $ full. The other box, which is twice as large as the first, is $\frac { 1 }{ 4 } $ full. He decides to combine the boxes into one.

Which box should he use, and how full will the box be?