In the diagram, three circles of radius 10 are tangent to each other and to a plane in three-dimensional space. Each of the circles is inclined at 45^\circ to the plane. There are three points where the circles touch each other. These three points lie on a circle parallel to the plane. The radius of this circle is closest to
Answer Choices
A. 6.9
B. 7.1
C. 7.3
D. 7.5
E. 7.7