Number of words in mumbo-jumbo tribe's language

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A tribe named Mumbo-Jumbo has $3$ letters in their alphabet, how many words are there with length no greater than $4$? I answered $3^4+3^3+3^2+3^1$. The author's answer is $40$, did the author add up $3^3+3^2+3^1+3^0$ by accident?