$(($solve it step by step with explaination and also write Decrypt part with detail $))$ Thank you

$1.$ The ciphertext below was encrypted using a substitution cipher. Decrypt the ciphertext without knowledge of the key.

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a$.$ Compute the relative frequency of all letters A$...$Z in the ciphertext. You may want to use a tool such as the open$-$source program CrypTool $[50]$ for this task. However, a paper and pencil approach is also still doable.

b$.$ Decrypt the ciphertext with the help of the relative letter frequency of the English language $($see Table $1\mathrm{.}1$ in Sect. $1\mathrm{.}2\mathrm{.}2).$ Note that the text is relatively short and that the letter frequencies in it might not perfectly align with that of general English language from the table.

c$.$ Who wrote the text?