Q=int(input())
for _ in range(Q):
  N,L=map(int,input().split())
  k=L//300+1
  G=[[] for i in range(300)]
  for i in range(N):
    x,y=map(int,input().split())
    pos=x//k
    G[pos].append((y,x))
  for i in range(300):
    G[i].sort()
  result=[]
  for i in range(300):
    for B in G[i]:
      y,x=B[:]
      result.append((x,y))
  print(len(result))
  for i in range(len(result)):
    x,y=result[i][:]
    print(x,y)