13, a, b, c are four distinct numbers and the HCF of each pair of numbers ( 13, a); (13, b); ( 13, c) is 13, where a, b, c are each less than 60 and a< b < c. What is the value of $$\frac{a+c}{b}$$?

A

5

B

2

C

3.5

D

4.5