  We study the problem of fairly allocating indivisible goods (positively
valued items) and chores (negatively valued items) among agents with decreasing
marginal utilities over items. Our focus is on instances where all the agents
have simple preferences; specifically, we assume the marginal value of an item
can be either $-1$, $0$ or some positive integer $c$. Under this assumption, we
present an efficient algorithm to compute leximin allocations for a broad class
of valuation functions we call order-neutral submodular valuations.
Order-neutral submodular valuations strictly contain the well-studied class of
additive valuations but are a strict subset of the class of submodular
valuations. We show that these leximin allocations are Lorenz dominating and
approximately proportional. We also show that, under further restriction to
additive valuations, these leximin allocations are approximately envy-free and
guarantee each agent their maxmin share. We complement this algorithmic result
with a lower bound showing that the problem of computing leximin allocations is
NP-hard when $c$ is a rational number.
