Operations research - summation notation

Operations research - summation notation

Outline: Hermione has been thinking about the imminent return of the Dark
Lord, so she has been busy packing her bag with all the items required for
her survival. Because she has so many different items, it is impossible to
list them all here; however she knows that she can formulate the problem
even without knowing those (trivial) details. She has $N$ items indexed
from $1$ to $N$; each item $x_i$ is associated with a value $c_i$, weight
$w_i$ and volume $v_i$. She cannot carry more than $W$ in weight, and the
bag can only hold up to $V$ in volume. Items must either be in the
backpack or not; i.e. we cannot put half a book in the bag! She needs to
maximize the value of the items that she is carrying, because she knows
she will not be able to replenish these for a very long time.
How would I formulate this problem using summation notation?