 
   getUsageAdjustment = (usageAdjustmentElement)->
     usageAdjustment = parseFloat usageAdjustmentElement.value
-    if isFiniteAndPositive usageAdjustment then usageAdjustment else 0
+    if isFiniteAndPositive(usageAdjustment) then usageAdjustment else 0
 
   setUsageSubsidy = (usageAdjustmentElement, usageSubsidy)->
     $(usageAdjustmentElement).parents("tr").find("span.minimum_cost").data("usageSubsidy", usageSubsidy.toFixed(2))

      # If we're hiding the value, store it so we can retreive it later
      $inputElement = $(this)
      $inputElement.data "original-value", $inputElement.val() if $inputElement.val()
      $inputElement.val if isDisabled then "" else $inputElement.data("original-value")
      $inputElement.prop "disabled", isDisabled

  deriveAdjustedCost = (unadjustedCost, usageSubsidyString)->

    interval += "s" if int_value > 1
    $("span.interval_replace").each -> $(this).html(interval)

  $interval.trigger('change')

  isFiniteAndPositive = (number)-> isFinite(number) && number > 0

