from fractions import Fraction

for _ in range(int(input())):
    n = int(input())
    arr = list(map(int, input().split()))
    
    def chk(k):
        ret = 0
        for t in arr:
            if t >= 0:
                ret += (t - k) ** 2
            else:
                ret += (t + k) ** 2
        return ret
    
    l, r = 0, int(1e9)
    while r - l > 3:
        lo = (l + r) // 2
        hi = lo + 1
        
        loVal = chk(lo / n)
        hiVal = chk(hi / n)
        if loVal < hiVal:
            r = hi
        else:
            l = lo
    
    alpha, ans = 0, 1e18
    for i in range(l, r + 1):
        tmp = chk(Fraction(i, n))
        if tmp < ans:
            ans = tmp
            alpha = i
    print(f'{ans.numerator}/{ans.denominator}')