N numbers, randomly generated between [0,1]
Make M operation,1/2probability to delete the maximum value,1/2probability to delete the minimum
value
Calculate the sum of expected value module 10 9 + 7
输入格式
Each test contains multiple test cases. The first line contains the number of test cases T(1 ≤ T ≤ 10000).
Description of the test cases follows.
The first line of each test case contains two integers n,m
1 ≤ m ≤ n ≤ 10 9
输出格式
For each test case, print one integer — the answer to the problem.