using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace cheap
{
    class Scanner
    {
        TextReader Reader;
        public Scanner(TextReader reader)
        {
            Reader = reader;
        }

        static int Index = 0;
        static string[] CurrentLine = { };

        public bool HasNext()
        {
            if (CurrentLine.Length == Index)
            {
                try
                {
                    CurrentLine = Reader.ReadLine().Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
                    Index = 0;
                    return HasNext();
                }
                catch (Exception e)
                {
                    return false;
                }
            }
            return true;
        }

        public String Next()
        {
            if (HasNext()) return CurrentLine[Index++];
            return null;
        }

        public int NextInt()
        {
            return int.Parse(Next());
        }

        public long NextLong()
        {
            return long.Parse(Next());
        }

        public float NextFloat()
        {
            return float.Parse(Next());
        }

        public double NextDouble()
        {
            return double.Parse(Next());
        }
    }

    class CheapestBuy
    {
        static void Main(string[] args)
        {
            Scanner inp = new Scanner(Console.In);
            int cases = inp.NextInt();
            for (int caseOn = 1; caseOn <= cases; caseOn++)
            {
                // number of Euros to the dollar
                double e = inp.NextDouble();
                // number of Pounds to the dollar
                double p = inp.NextDouble();

                int n = inp.NextInt();
                double cost = 0;
                for (int i = 0; i < n; i++)
                {
                    double usdcostEuro = inp.NextDouble() * e;
                    double usdcostPound = inp.NextDouble() * p;

                    if (usdcostEuro < usdcostPound)
                    {
                        cost += usdcostEuro;
                    }
                    else
                    {
                        cost += usdcostPound;
                    }
                }
                Console.WriteLine("{0:F2}$", cost);
            }

        }
    }
}