Let C $=($K$,$E$,$D$)$ be a cipher. Consider the cipher C$\text{'}=($K$\text{'},$E$\text{'},$D$\text{'}),$ where E$\text{'}$k $($P$)=$ Ek$($Ek$($P$)).$ Prove that for every CPA secure ciphers C $,$ the cipher C$\text{'}$ is also CPA secure$.$ That is$,$ show that for every CPA adversary A attacking C$\text{'}$ there is a CPA adversary B attacking C with about the same advantage and running time.