To find the amount spent on marketing that will achieve the maximum profit for the given profit function \( P = -4x^2 + 800x + 3000 \), we can use the vertex formula for a quadratic function. The vertex \( x \) of a parabola represented in the standard form \( P = ax^2 + bx + c \) occurs at the value:
\[ x = -\frac{b}{2a} \]
In this case, the coefficients are:
- \( a = -4 \)
- \( b = 800 \)
Now, substituting these values into the vertex formula:
\[ x = -\frac{800}{2 \times -4} = -\frac{800}{-8} = 100 \]
Therefore, the amount directed toward marketing to achieve the maximum profit is \( x = 100 \) (in thousands of dollars).
Thus, the spending directed toward marketing to achieve the maximum profit is $100,000.