PlaceOrder.cs

public class PlaceOrder
{
    private readonly TimeProvider _timeProvider;

    public PlaceOrder(TimeProvider timeProvider)
    {
        _timeProvider = timeProvider;
    }
    public Order Process()
    {
        var now = _timeProvider.GetUtcNow();
        var total = now.DayOfWeek == DayOfWeek.Friday ? 50 : 100;
        return new Order(now, total);
    }    
}