# Enter your code here. Read input from STDIN. Print output to STDOUT
import operator
for _ in range(input()):
    n = input()
    arr = []
    for i in range(n):
        x, y = map(int, raw_input().strip().split())
        arr.append((x, y))
    arr.sort(key = operator.itemgetter(0, 1))
    
    x1, y1 = arr[0]
    x4 = arr[-1][0]
    y4 = max(arr, key = operator.itemgetter(1))[1]
    
    ##x4, y4 = arr[-1]
    ##x2, y2 = x4, y1
    ##x3, y3 = x1, y4
    """
    print " arr = ", arr
    print " x1, y1 = ", x1, y1
    print " x4, y4 = ", x4, y4
    print "----------------"
    """
    for i, j in arr:
        """
        print " i = ", i
        print " j = ", j
        print "----------------"
        """
        f = 0
        if i == x1 or i == x4 or j == y1 or j == y4:
            if j == y1 or j == y4 or i == x1 or i == x4:
                continue
            else:
                f = 1
                break
        else:
            f = 1
            break
        break
    print "YES" if f == 0 else "NO"