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The total cost \(C(x)\) (in rupees) for producing \(x\) units of an item is given by:
\[C(x) = 0.007x^3 - 0.003x^2 + 15x + 4000\]

We are asked to find the marginal cost when \(x = 17\).\[\]
Marginal cost is the rate of change of total cost with respect to the number of units produced, i.e.,

\(MC = \dfrac{dC}{dx}\)
\[\]

Differentiate \(C(x)\):

\[\dfrac{dC}{dx} = 0.007 \cdot 3x^2 - 0.003 \cdot 2x + 15 = 0.021x^2 - 0.006x + 15\]

Now, substitute \(x = 17\):

\[MC = 0.021 \cdot 17^2 - 0.006 \cdot 17 + 15 = 0.021 \cdot 289 - 0.006 \cdot 17 + 15\]

\[= 6.069 - 0.102 + 15 = 20.967\]

Final Answer:
When 17 units are produced, the marginal cost is Rs. 20.967