Abakery sells a pack of peanut butter cookies for $3 and a
pack of chocolate chip cookies for $5. if the bakery
sells x packs of peanut butter cookies and y packs of
chocolate chip in a month, what is the objective
function f(x, y) for that month's revenue in terms of x and y
f(x, y) = 5x + 3y
f(x, y) = 3x + 5y
f(x, y) = x + y
f(x, y) = x - y