Beth has a collection of 8 boxes of clothing for a charity, and the average (arithmetic mean) number of pieces of clothing per box is c. If she replaces a box in the collection that has 12 pieces of clothing with a box that contains 22 pieces of clothing, what is the average number of pieces of clothing per box for the new collection in terms of c? $$\left(A\right)\ c-\frac{5}{4}$$ $$\left(B\right)\ c+\frac{5}{4}$$ $$\left(C\right)\ 8-\frac{10}{c}$$ $$\left(D\right)\ 8+\frac{10}{c}$$ $$\left(E\right)\ 8c-10$$ [spoiler]OA=B[/spoiler].

I am really confused here. I don't know how to set the equations for solving this PS question. <i class="em em-sob"></i>