Consider the following premises. For all x_15, if x_15 were happy, then x_15 is writing a letter. There is at least one x_15 for which if x_15 makes tea, then x_15 is writing a letter. For all x_15, x_15 is not happy. For all x_15, x_15 will make tea or x_15 will take a plane. For all x_15, if x_15 writes a letter, then x_15 is happy. For all x_15, if x_15 writes a letter, then x_15 is making tea. Can we infer the following from them? If we can, name the inference rule being used: For all x_15, if x_15 writes a letter, then x_15 is making tea.
That is one of the premises. Therefore, the answer is yes.