Recently,I
Recently, I have readed brendle's artical"between p-point read Brendle's article Between p-points and nowhere dense ultrafilters" [Isr. J. Math. 113, 205-230]. In this paper,he paper, he noted that cof(C,M)=cov(M).Where C repsent closre $\mathrm{cof}(\mathcal{C},\mathcal{M}) = \mathrm{cov}(\mathcal{M})$, where $\mathcal{C}$ represents the set of all closed countable subset subsets of the real line. But I don't know how to proof,a prove this; a proof sketch will would be appreciated.
I also want to know cof(C',M),Where C' repsent about $\mathrm{cof}(\mathcal{C}',\mathcal{M})$, where $\mathcal{C}'$ represents the set of all countable subset subsets of the real line.

