func main()
	var t: int :: cui@inputInt()
	for(1, t)
		var l: int :: cui@inputInt()
		var r: int :: cui@inputInt()
		var a: int :: cui@inputInt()
		var b: int :: cui@inputInt()
		var ans: int :: lib@max(a * l + b, a * r + b)
		do cui@print("\{ans}\n")
	end for
end func