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Solution

Given:
Number of processes = 4
Maximum resources required by each process = 5

Formula used to avoid deadlock:
$R_{min} = n(m - 1) + 1$

Substitute values:
$R_{min} = 4(5 - 1) + 1$
$R_{min} = 4 \times 4 + 1$
$R_{min} = 16 + 1 = 17$

Final Answer:
Minimum number of units of resource R required = $17$