B"You are given four integers n , B , x and y . You should build a sequence a_0, a_1, a_2, ... , a_n where a_0 = 0 and for each i ge 1 you can choose: Your goal is to build such a sequence a that a_i <= B for all i and sum limits_{i=0}^{n}{a_i} is maximum possible. The first line contains a single integer t ( 1 <= t <= 10^4 ) -- the number of test cases. Next t cases follow. The first and only line of each test case contains four integers n , B , x and y ( 1 <= n <= 2 cdot 10^5 ; 1 <= B, x, y <= 10^9 ). It's guaranteed that the total sum of n doesn't exceed 2 cdot 10^5 . For each test case, print one integer -- the maximum possible sum limits_{i=0}^{n}{a_i} . In the first test case, the optimal sequence a is [0, 1, 2, 3, 4, 5] . In the second test case, the optimal sequence a is [0, 10^9, 0, 10^9, 0, 10^9, 0, 10^9] . In the third test case, the optimal sequence a is [0, -3, -6, 1, -2] . "...