Triangle A B C, with sides of length 5,6 , and 7 , has one vertex on the positive x-axis, one on the positive y-axis, and one on the positive z-axis. Let O be the origin. What is the volume of tetrahedron O A B C ?
Answer Choices
A. \sqrt{85}
B. \sqrt{90}
C. \sqrt{95}
D. 10
E. \sqrt{105}