In a duct system, three equal pipes, with external radius 30 cm, are welded together and placed inside a pipe with larger radius, of measure R. For later easy maintenance, there must be a distance of 10 cm between the welded pipes and the larger radius pipe. This distance is guaranteed by a metal spacer, as shown in the figure.
Use 1.7 as an approximation for $\sqrt{3}$. The value of R, in centimeters, is equal to
(A) 64.0.
(B) 65.5.
(C) 74.0.
(D) 81.0.
(E) 91.0.