Xiao Hua is a student who loves running. However, he is too fat to run fast.

As a straight A student of science and engineering, Xiao Hua developed a running-helper one day to accelerate himself while running. He called it the HKJA(Hong Kong Journalist Accelerator).

The HKJA’s operating mechanism is as follows: each acceleration contains n independent sections (where n is a non-negative random variable). Its expectation is μ_n and the variance is σ_n² . During the i^th independent acceleration-section, the HKJA gives the user a velocity increment values a_i(where a_i~N(μ_a.σ_a²) ). All the a_i is in i.i.d.(independent identical distribution). The result of the final acceleration is the sum of all a_i  , denoted as S.

                                                                          

It is not difficult to find that the total speed increment S is also a random variable.

In order to test whether the acceleration effect is "steady", Xiao Hua would like to know, given the features of distribution which n and ai obey (given the expectations and variance), how much is the variance of random variable S ?

The first line of the input file is a positive integer T（1<=T<=20），indicating that there are T test cases.

As for each test case：there is only one line contains four integers representing μ_n，σ_n²，μ_a，σ_a².

0<|μ_a|<=100, 0<=μ_n,σ_n,σ_a<=100.

For each set of samples, output the variance of the random variable S.

4
2 0 10 4
2 3 6 4
5 2 -5 3
3 4 3 0

8
116
65
36

Standard input and output.

 n~N(μ,σ²)means random variable nobeys normal distribution. The expectation is μ, the variance is σ²，it is obvious that the variance isnon-negative.