Optimizing cost on Turo

turoMiles.js

function turoMiles(desiredMiles) {
  var costPerDay = 35;
  var costPerMileOver = 0.75;
  var milesPerDay = 150;
  var milesPerWeek = 1000;

  function milesAllowed(days) {
    var weeks = Math.floor(days / 7);
    days = days % 7;
    return weeks*milesPerWeek + days*milesPerDay;
  }

  var entries = [];
  for (var days=5; days<=11; days++) {
    var limit = milesAllowed(days);
    var overage = Math.max(0, desiredMiles - limit);
    var cost = days*costPerDay + overage*costPerMileOver;
    entries.push({
      days: days,
      limit: limit,
      overage: overage,
      cost: cost,
    });
  }

  console.table(entries);
}