The answer is A.
First we substitute 8 into the given equation.
[tex]s = 10 \sqrt{4(8)} +15 [/tex]
Multiply 8 and 5, then find the square root of 40. Finally multiply it by 10.
[tex]s = 10 \sqrt{40} +15 [/tex]
[tex]s = 63.245 +15 [/tex]
Then add 15.
And the answer will be 78.245.
Now the question says that s is in thousands, so the real answer would be about 75,000.
