Is using the same key twice in one$-$time pad secure $($i$.$e$.,$ Encryption: $Mo+Ko+K=C$;

Decryption: $Co+Ko+K=M?$ Why? Please explain in detail. $($hint: you should explain

if $P(M|C)?=P(M)$ by using mathematical proof. Only textual explanation without the

inclusion of mathematical formulas will result in an incomplete analysis and, therefore,

may lead to a deduction in grading.$)$