Machines \(A\) and \(B\) always operate independently and at their respective constant rates. When working alone, Machine \(A\) can fill a production lot in \(5\) hours, and Machine \(B\) can fill the same lot in \(x\) hours. When the two machines operate simultaneously to fill the production lot, it takes them \(2\) hours to complete the job. What is the value of \(x?\)

(A) \(3 \frac13\)

(B) \(3\)

(C) \(2 \frac12\)

(D) \(2 \frac13\)

(E) \(1 \frac12\)

Answer: A

Source: Official Guide