Problem

R_1

is the circumradius of the pedal triangle of a given triangle and

R_2

is the circumradius of the pedal triangle of the pedal triangle formed, and so on

R_3, R_4, \dots

, then the value of

\sum_{i=1}^{\infty} R_i

, where

R

(circumradius) of

\Delta ABC

is 5 is a. 8 b. 10 c. 12 d. 15