Philosophy Question! PLEASE HELP ME!?

Nope, sorry. Your teacher wants to read your answers, not ours. Perhaps someone in the HOMEWORK HELP  forum will take more pity, lazybones. 

J153e just taught me so much.  I think it should help you.   Please award him the BA.   

It may be that your instructor prefers utility over Kant's more nuanced and yet clearer understanding of happiness; imho, Kant's understanding is more profound than either Mill's (or Aristotle's).

Mill:  If it feels good, do it; the maximum feel-good for the maximum citizenry = optimal utility.

(Aristotle:  eudaimonia or best happiness for mankind is contemplation.)

In contrast to both (and also re your instructor's positing), Kant has no "difficulty" in defining happiness; rather, he defines it well in his "The Metaphysical Principles of Virtue":  "...[happiness is]...continuous well-being, enjoyment of life, complete satisfaction with one's condition."  To be truly happy, Kant must know himself clearly.  This is more profound than "it feels good" or "think a lot."

Imho, a critique of Kant's bifurcate happiness/morality may be made, in the manner of Hegel's critique of Kant's bifurcation of Noumenon and phenomena:  namely, Kant does not go far enough in his psychological clarification to understand similar happiness processes are operant in humankind; Maslow does this unification:  https://en.wikipedia.org/wiki/Maslow's_hierarchy_o...

If Kant had proceeded in this manner, his Categorical Imperative would be applicable to both morality and happiness.

As Kant did not proceed thusly, his mode splays out as a circle of universal rational morality, with each individual's clear perception of their particular happiness constituting a point (or, smaller circle) somewhere within the universal rationality of the CI.  To iterate, if Kant had unified universal moral rationality with universal (maslowian) being-cognition, then there would splay two overlapping circles, one of CI, and one of CI as "know thyself as being-cognition" (with subsets of fields of being-cognition within the general, universal schema of being-cognition). 

As for Mill, he blesses pleasure, and eschews pain, re happiness; yet, he posits that humans will choose the higher pleasure-choices over the lower; this is contradicted in various histories.  (Aristotle posited that higher happiness was in part generated by an exercise of virtue; Mill seems to downplay this need for such exercise, or merely take it as a given.)