Which of the following is the best estimate for the monthly mean numb…

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Sunspots are temporary dark spots on the surface of the Sun. The monthly mean number of sunspots for one calendar month is the average of the number of sunspots observed each day during the month. The linear function

s

models the monthly mean number of sunspots as a function of the number of months,

x

, since April 2015, where

0 \leq x \leq 30

. The graph of

y = s (x)

is shown.

Which of the following is the best estimate for the monthly mean number of sunspots in April 2016?