public void RemoveSales(SalesRecord sr)
 {
     Sales.Remove(sr);
 }
 public double TotalSales(DateTime initial, DateTime final)
 {
     return(Sales.Where(sr => sr.Date >= initial && sr.Date <= final).Sum(sr => sr.Amount));
 }
 public void AddSales(SalesRecord sr)
 {
     Sales.Add(sr);
 }