Bob has an account in the Bobby Bank. His current account balance is W rupees.

Each month, the office in which Bob works deposits a fixed amount of X rupees to his account.
Y rupees is deducted from Bob's account each month as bank charges.

Find his final account balance after Z months. Note that the account balance can be negative as well.

------ Input Format ------

• The first line will contain T, the number of test cases. Then the test cases follow.
• Each test case consists of a single line of input, containing four integers W,X,Y, and Z — the initial amount, the amount deposited per month, the amount deducted per month, and the number of months.

------ Output Format ------

For each test case, output in a single line the final balance in Bob's account after Z months.

------ Constraints ------

$1 ≤ T ≤ 1000$
$1 ≤ W,X,Y,Z ≤ 10^{4}$

----- Sample Input 1 ------
3
100 11 1 10
999 25 36 9
2500 100 125 101

----- Sample Output 1 ------
200
900
-25
----- explanation 1 ------
Test case $1$: Bob's current account balance is $100$. At the end of each month Bob gets Rs $11$ and pays Rs $1$, thus gaining $10$ per month. Thus, at the end of $10$ months, Bob will have $100 + 10 \times 10 = 200$.

Test case $2$: Bob's current account balance is $999$. At the end of each month Bob gets Rs $25$ and pays Rs $36$, thus losing $11$ per month. Thus, at the end of $9$ months, Bob will have $999 - 11 \times 9 = 900$.

Test case $3$: Bob's current account balance is $2500$. At the end of each month Bob gets Rs $100$ and pays Rs $125$, thus losing $25$ per month. Thus, at the end of $101$ months, Bob will have $2500 - 25 \times 101 = -25$.

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