11. Fruit Shop

using System;

namespace FruitShop
{
    class Program
    {
        static void Main(string[] args)
        {
            string fruit = Console.ReadLine();
            string day = Console.ReadLine();
            double quantity = double.Parse(Console.ReadLine());

            if (day == "Monday" || day == "Tuesday" || day == "Wednesday" || day == "Thursday" || day == "Friday")
            {
                if (fruit == "banana")
                {
                    Console.WriteLine($"{2.5 * quantity:F2}");
                }
                else if (fruit == "apple")
                {
                    Console.WriteLine($"{1.2 * quantity:F2}");
                }
                else if (fruit == "orange")
                {
                    Console.WriteLine($"{0.85 * quantity:F2}");
                }
                else if (fruit == "grapefruit")
                {
                    Console.WriteLine($"{1.45 * quantity:F2}");
                }
                else if (fruit == "kiwi")
                {
                    Console.WriteLine($"{2.7 * quantity:F2}");
                }
                else if (fruit == "pineapple")
                {
                    Console.WriteLine($"{5.5 * quantity:F2}");
                }
                else if (fruit == "grapes")
                {
                    Console.WriteLine($"{3.85 * quantity:F2}");
                }
                else
                {
                    Console.WriteLine("error");
                }
            }

            else if (day == "Saturday" || day == "Sunday")
            {
                if (fruit == "banana")
                {
                    Console.WriteLine($"{2.7 * quantity:F2}");
                }
                else if (fruit == "apple")
                {
                    Console.WriteLine($"{1.25 * quantity:F2}");
                }
                else if (fruit == "orange")
                {
                    Console.WriteLine($"{0.9 * quantity:F2}");
                }
                else if (fruit == "grapefruit")
                {
                    Console.WriteLine($"{1.6 * quantity:F2}");
                }
                else if (fruit == "kiwi")
                {
                    Console.WriteLine($"{3 * quantity:F2}");
                }
                else if (fruit == "pineapple")
                {
                    Console.WriteLine($"{5.6 * quantity:F2}");
                }
                else if (fruit == "grapes")
                {
                    Console.WriteLine($"{4.2 * quantity:F2}");
                }
                else
                {
                    Console.WriteLine("error");
                }
            }
            else
            {
                Console.WriteLine("error");
            }
        }
    }
}

РЕШЕНИЕ С ТЕРНАРЕН ОПЕРАТОР:

using System;

namespace FruitShop
{
    class Program
    {
        static void Main(string[] args)
        {
            string fruit = Console.ReadLine();
            string day = Console.ReadLine();
            double quantity = double.Parse(Console.ReadLine());

            double totalSum =
                (day == "Monday" || day == "Tuesday" || day == "Wednesday" || day == "Thursday" || day == "Friday" ?
                (fruit == "banana" ? 2.5 : fruit == "apple" ? 1.2 : fruit == "orange" ? 0.85 : fruit == "grapefruit" ? 1.45
                : fruit == "kiwi" ? 2.7 : fruit == "pineapple" ? 5.5 : fruit == "grapes" ? 3.85 : 0) :
                day == "Saturday" || day == "Sunday" ?
                (fruit == "banana" ? 2.7 : fruit == "apple" ? 1.25 : fruit == "orange" ? 0.9 : fruit == "grapefruit" ? 1.6
                : fruit == "kiwi" ? 3 : fruit == "pineapple" ? 5.6 : fruit == "grapes" ? 4.2 : 0) : 0) * quantity;

            Console.WriteLine(totalSum == 0 ? "error" : $"{totalSum:F2}");
        }
    }
}