Conisder a mechanism in which a single reactant profuces several Products by the following parallel first order reactions :
`A overset(k_(1))rarrB, A overset(k_(2))rarrC A overset(k_(3))rarrD`
Write the rate expresison for `[A]`.

Explanation

To derive the rate expression for the concentration of reactant A in the given parallel first-order reactions, we can follow these steps:

### Step 1: Identify the reactions
We have three parallel reactions:
1. \( A \overset{k_1}{\rightarrow} B \)
2. \( A \overset{k_2}{\rightarrow} C \)
3. \( A \overset{k_3}{\rightarrow} D \)

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