12) log128 (0,25)^log81(1/3+1/9+1/27+...)

log128(0.25)^(log81(1/3 + 1/9 + 1/27 + ...)) = log128(0.25)^(log81(1/2)) = log128(0.25)^(-1/log(1/2)81) = log128(0.25)^(-1/log(1/2)3^4) = log128(0.25)^(-1/(4log(1/2)3))