Consider the following premises. For all x_12, if x_12 writes a letter, then x_12 is sleeping. There is at least one x_12 for which x_12 will write a letter if and only if x_12 is a musician. For all x_12, if x_12 sleeps, then x_12 is a musician. Can we infer the following from them? For all x_12, the fact that x_12 sleeps does not imply that x_12 is a musician.
That contradicts the premises. Therefore the answer is no.