package Test4;
import java.util.ArrayList;
import java.util.Scanner;

// 之前用int 好像是90%，改了long 就100%了，应该大概是这样的
public class Main6 {

    public static void main(String[] args) {

        Scanner scanner=new Scanner(System.in);
        int t=scanner.nextInt();
        for (int i=0;i<t;i++){

            long A=scanner.nextLong();
            long B=scanner.nextLong();
            long p=scanner.nextLong();
            long q=scanner.nextLong();
         

            int sum=0;

            while (A<B){

                if(A+p<B){

                    while (A+p<B){

                        p=p*q;
                        sum++;
                    }
                    A=A+p;
                    sum++;

                }else {
                    A=A+p;
                   
                }


            }
            System.out.println(sum);

        }




    }


}