B'Pak Chanek is the chief of a village named Khuntien. On one night filled with lights, Pak Chanek has a sudden and important announcement that needs to be notified to all of the n residents in Khuntien. First, Pak Chanek shares the announcement directly to one or more residents with a cost of p for each person. After that, the residents can share the announcement to other residents using a magical helmet-shaped device. However, there is a cost for using the helmet-shaped device. For each i , if the i -th resident has got the announcement at least once (either directly from Pak Chanek or from another resident), he/she can share the announcement to at most a_i other residents with a cost of b_i for each share. If Pak Chanek can also control how the residents share the announcement to other residents, what is the minimum cost for Pak Chanek to notify all n residents of Khuntien about the announcement? Each test contains multiple test cases. The first line contains an integer t ( 1 <= q t <= q 10^4 ) -- the number of test cases. The following lines contain the description of each test case. The first line contains two integers n and p ( 1 <= q n <= q 10^5 ; 1 <= q p <= q 10^5 ) -- the number of residents and the cost for Pak Chanek to share the announcement directly to one resident. The second line contains n integers a_1,a_2,a_3, ldots,a_n ( 1 <= q a_i <= q10^5 ) -- the maximum number of residents that each resident can share the announcement to. The third line contains n integers b_1,b_2,b_3, ldots,b_n ( 1 <= q b_i <= q10^5 ) -- the cost for each resident to share the announcement to one other resident. It is guaranteed that the sum of n over all test cases does not exceed 10^5 . For each test case, output a line containing an integer representing the minimum cost to notify all n residents of Khuntien about the announcement. In the first tes'...