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The sum of $n$ terms of the series $4+44+444+\ldots .$ is

1. $(4 / 81)\left[10^{\mathrm{n}+1}-9 \mathrm{n}-1\right]$
2. $(4 / 81)\left[10^{n-1}-9 n-1\right]$
3. $(4 / 81)\left[10^{n+1}-9 n-10\right]$
4. $(4 / 81)\left[10^{\mathrm{n}}-9 \mathrm{n}-10\right]$