import java.util.Arrays;
import java.util.Scanner;

public class Solution {
    static int gasStations;
    static Long maxFuel;
    static Long startingFuel;
    static Long length;

    private static class Station implements Comparable<Station> {
        long  price;
        long  pos;

        private Station(long  price, long pos) {
            this.price = price;
            this.pos = pos;
        }

        @Override
        public int compareTo(Station o) {
            return Long.valueOf(price).compareTo(o.price);
        }

        @Override
        public String toString() {
            return "{" + price + "$, " + pos + "}";
        }
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int M = Integer.parseInt(scanner.nextLine());
        for (int i = 0; i < M; i++) {
            String[] line = scanner.nextLine().split("\\s+");
            gasStations = Integer.parseInt(line[0]);
            maxFuel = Long.parseLong(line[1]);
            startingFuel = Long.parseLong(line[2]);
            length = Long.parseLong(line[3]);
            Station[] stations = new Station[gasStations];
            for (int s = 0; s < gasStations; s++) {
                line = scanner.nextLine().split("\\s+");
                stations[s] = new Station(Long.parseLong(line[1]), Long.parseLong(line[0]));
            }
            //SORTING STATIONS, CHEAPEST FIRST
            Arrays.sort(stations);
            checkSolution(stations);
        }

    }

    private static void checkSolution(Station[] stations) {
        long[] reserveFuel = {0};
        System.out.println(recursiveCall(0, length, startingFuel, stations, reserveFuel));
    }

        // RETURNS THE $$ SPENT IN FUEL
    // PARAMS:
    //  START: the start point of this part of the trip
    //  END: the goal of this part of the trip
        //  FUEL: the amount of fuel I have for this section
    //  STATIONS: all the stations, nulled out the ones I have been to
    //  RESERVE FUEL: pointer used to return the amount of gas that was left after the trip. /*I'm not proud of this*/
    private static long recursiveCall(long start, long end, long fuel, Station[] stations, long [] reserveFuel) {
//      System.out.println("RECURSIVING -- start:" + start + " end:" + end + " fuel:" + fuel);
            // IF I HAVE ENOUGH FUEL TO GET TO THE END
        if (end - start <= fuel) {
            reserveFuel[0] = fuel - (end - start);
            return 0; //SPENT NO CASH, I COULD GET THERE WITH THE CURRENT TANK
        }

        Station station = null;
        for (int s = 0; s < gasStations && station == null; s++) {
                // GET THE FIRST (AND CHEAPEST) STATION BETWEEN MY CURRENT START AND END POSITIONS
            if (stations[s] != null && stations[s].pos >= start && stations[s].pos < end) {
                station = stations[s];
                stations[s] = null; //NULLING OUT USED STATIONS
            }
        }
            // THERE ARE NO STATIONS BETWEEN START AND END
        if (station == null) {
            return -1; // CAN'T GET THERE
        }
        long ans = 0; // TOTAL $ SPENT

            long var = recursiveCall(start, station.pos, fuel, stations, reserveFuel);
            // IF I COULDN'T MAKE IT
        if(var == -1)
            return var;

            ans += var; // ADDING THE $$ NEEDED TO GET HERE

            long neededFuel = Math.min(maxFuel- reserveFuel[0], end - station.pos - reserveFuel[0]);

            long chargedFuel = reserveFuel[0] + neededFuel;
        ans += (neededFuel * station.price); // ADDING WHAT I SPENT HERE

//      System.out.println("CHARGING FUEL -- $" + (neededFuel * station.price) + " in:" + station.pos);
        reserveFuel[0] = 0;
        var = recursiveCall(station.pos, end, chargedFuel, stations, reserveFuel);
            // IF I COULDN'T MAKE IT
        if(var == -1)
            return var;

            ans += var; // ADDING WHAT I WILL SPEND IN THE REST OF THE TRIP TO MY GOAL
        return ans;
    }
}