Packet X contains pens, pencils and erasers in the ratio 1:2:3. Packet Y contains pens and pencils in the ratio 4:5. If the total number of pens and pencils in both the packets combined is 13 and 20 respectively, what is the number of erasers in Packet X?

A. 5
B. 6
C. 15
D. 18
E. 20