use std::io::Read;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	s.trim().split('\n').skip(1).for_each(|c| {
		let n: Vec<i32> = c.split_whitespace().flat_map(str::parse).collect();
		println!("{}", (n[0] * n[2]).max(n[1] * n[2]) + n[3]);
	});
}