Solve the programming task below in a Python markdown code block.
Read problem statements in [Vietnamese],
[Bengali], [Mandarin Chinese], and [Russian] as well. 

Chef is planning a heist in the reserve bank of Chefland. They are planning to hijack the bank for $D$ days and print the money. The initial rate of printing the currency is $P$ dollars per day and they increase the production by $Q$ dollars after every interval of $d$ days. For example, after $d$ days the rate is $P+Q$ dollars per day, and after $2d$ days the rate is $P+2Q$ dollars per day, and so on. Output the amount of money they will be able to print in the given period.

------ Input ------

The first line contains an integer $T$, the number of test cases. Then the test cases follow. 
Each test case contains a single line of input, four integers $D, d, P, Q$. 

------ Output ------
For each test case, output in a single line the answer to the problem.

------ Constraints  ------
$1 ≤ T ≤ 10^{5}$
$1 ≤ d ≤ D ≤ 10^{6}$
$1 ≤ P, Q ≤ 10^{6}$

------ Subtasks ------
Subtask #1 (15 points): $d ≤ D ≤ 100$

Subtask #2 (85 points): original constraints

----- Sample Input 1 ------ 
3

2 1 1 1

3 2 1 1

5 2 1 2
----- Sample Output 1 ------ 
3

4

13
----- explanation 1 ------ 
Test Case $1$: 
- On the first day, the rate of production is $1$ dollar per day so $1$ dollar is printed on the first day.  
- On the second day, the rate of production is $1 + 1 = 2$ dollars per day so $2$ dollars are printed on the second day.
- The total amount of money printed in $2$ days is $1 + 2 = 3$ dollars.

Test Case $2$: 
- For the first two days, the rate of production is $1$ dollar per day so $1 \cdot 2 = 2$ dollars are printed on the first two days.  
- On the third day, the rate of production is $1 + 1 = 2$ dollars per day so $2$ dollars are printed on the third day.
- The total amount of money printed in $3$ days is $2 + 2 = 4$ dollars.

Test Case $3$: 
- For the first two days, the rate of production is $1$ dollar per day so $1 \cdot 2 = 2$ dollars are printed on the first two days.  
- On the next two days, the rate of production is $1 + 2 = 3$ dollars per day so $3 \cdot 2 = 6$ dollars are printed on the next two days.
- On the last day, the rate of production is $3 + 2 = 5$ dollars per day so $5$ dollars are printed on the last day.
- The total amount of money printed in $5$ days is $2 + 6 + 5 = 13$ dollars.