The rotor of an AC generator is driven so that its speed doubles. Which of the following correctly describes the resulting changes in (i) the frequency of the generated emf and (ii) its maximum value?
(a) Frequency becomes twice its original value but maximum emf remains the same.
(b) Both frequency and maximum emf become twice their original values.
(c) Frequency becomes twice its original value but maximum emf becomes four times its original value.
(d) Frequency remains the same, but maximum emf becomes twice its original value.