Give the systematic IUPAC names of the following compounds :
` HC -= C - underset(C_2 H_5 ) underset(|) overset(CH_3) overset(|)C-CH_2 - CH = CH_2`

Explanation

To determine the systematic IUPAC name of the given compound, we will follow these steps:

### Step 1: Identify the Longest Carbon Chain
First, we need to identify the longest continuous carbon chain in the compound. The compound has a total of 6 carbon atoms in the main chain.

### Step 2: Number the Carbon Chain
Next, we will number the carbon chain. According to IUPAC rules, we should give priority to the double bond over the triple bond when numbering. Therefore, we will start numbering from the end of the chain closest to the double bond.

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