Consider the following premises. There is at least one y for which y is a taxi driver if and only if y is bored. For all y, y is a taxi driver if and only if y is bored. Can we infer the following from them? If we can, name the inference rule being used: For all y, if is not true that y is bored if and only if y is a taxi driver.
That contradicts the premises. Therefore the answer is no.