$$X$$ is $$7^{th}$$ from the top while $$Y$$ is $$16^{th}$$ from the bottom in the class ranking. If they interchange their positions, then $$X$$ becomes $$21^{st}$$ from the top. What will be the position of $$Y$$ from the bottom?

A

$$16^{th}$$

B

$$29^{th}$$

C

$$21^{th}$$

D

$$30^{th}$$