private decimal FullCostOfBand(PriceBand band)
{
var totalMessagesInBand = band.QtyTo.Value - (band.QtyFrom - 1);
return(totalMessagesInBand * band.PricePerTextMessage);
}
private decimal PartialCostOfBand(PriceBand band, int totalMonthlyMessages)
{
var totalMessagesSentInBand = totalMonthlyMessages - (band.QtyFrom - 1);
return(totalMessagesSentInBand * band.PricePerTextMessage);
}
private decimal CalculateCostOfBand(PriceBand band, int totalMonthlyMessages)
{
return(band.QtyTo.HasValue && totalMonthlyMessages > band.QtyTo
? FullCostOfBand(band)
: PartialCostOfBand(band, totalMonthlyMessages));
}