Pareto optimal routes

A wholesale carrier publishes thousands of interconnect routes to the same destination. Route i charges setup_fees[i] cents to open a call plus rates[i] cents for every minute the call lasts, so a call of t minutes costs setup_fees[i] + rates[i] * t cents. A duration is any value at or above zero and need not be a whole number of minutes. The sales page should carry only routes a customer could rationally pick, so route i belongs on it when some duration exists at which it costs strictly less than every other route. A route that only ever ties for cheapest does not belong. The two lists have the same length and hold values at or above zero. Return the indices of the routes that belong, in increasing order, or an empty list when none do.