using System.Collections.Generic;

public class ChestsGenerator
{
    public List<int> Rewards { get; private set; }

    private readonly int[] _avaibles = { 50, 150, 300 };

    public ChestsGenerator()
    {
        Rewards = new List<int>(9);

        for (int i = Rewards.Capacity; i > 0; i--)
            Rewards.Add(_avaibles[i % 3]);

        Rewards.Shuffle();
    }
}