package main

import "fmt"

func main() {
	var q int64
	fmt.Scan(&q)
	for i := int64(0); i < q; i++ {
		var k, n, a, b int64
		fmt.Scan(&k, &n, &a, &b)
		d := a - b
		temp := k - 1
		nb := n * b
		if nb > temp {
			fmt.Println(-1)
		} else {
			numa := temp - nb
			x := numa / d
			if x > n {
				x = n
			}
			fmt.Println(x)
		}
	}
}