Machine \(A,\) working alone at a constant rate, can complete a certain production lot in \(x\) hours. Machine \(B,\)

Machine \(A,\) working alone at a constant rate, can complete a certain production lot in \(x\) hours. Machine \(B,\) working alone at a constant rate, can complete \(\dfrac15\) of the same production lot in \(y\) hours. Machines \(A\) and \(B,\) working together, can complete \(\dfrac12\) of the same production lot in \(z\) hours. What is the value of \(y\) in terms of \(x\) and \(z?\)

A. \(\dfrac{5x - 10z}{2xz}\)
B \(\dfrac{2xz}{5x - 10z}\)
C. \(\dfrac{5xz}{x + z}\)
D. \(\dfrac{xz}{x} + z\)
E. \(\dfrac{xz}{x} + 2z\)

Answer: B

Source: Manhattan GMAT