T = int(input())
X, Y = [], []
for t in range(T):
    isRect = True
    N = int(input())
    for i in range(N):
        x, y = [int(s) for s in input().split(" ")]
        X.append(x)
        Y.append(y)
    
    xl, xr = min(X), max(X)
    yl, yr = max(Y), max(Y)
 
    for x,y in zip(X, Y):
        if not (x == xl or x == xr or y == yl or y == yr):
            isRect = False
            break
    if isRect:
        print("YES")
    else:
        print("NO")