Consider the following premises. For all y_4, if y_4 were a musician, then y_4 is curious. For all y_4, y_4 is curious if and only if y_4 is a musician. Can we infer the following from them? If we can, name the inference rule being used: For all y_4, if y_4 were a musician, then y_4 is curious.
That is one of the premises. Therefore, the answer is yes.