Question 55
The numbers $2, b, c, d, 72$ are listed in increasing order so that $2, b, c$ form an arithmetic sequence, $b, c, d$ form a geometric sequence, and $c, d, 72$ form a harmonic sequence (that is, a sequence whose reciprocals of its terms form an arithmetic sequence). What is the value of $b+c$ ?
(a) 7
(b) 13
(c) 19
(d) 25
(a) 7
(b) 13
(c) 19
(d) 25