Gru has a string $S$ of length $N$, consisting of only characters $a$ and $b$ for banana and $P$ points to spend.
Now Gru wants to replace and/or re-arrange characters of this given string to get the lexicographically smallest string possible. For this, he can perform the following two operations any number of times.
1) Swap any two characters in the string. This operation costs $1$ $point$. (any two, need not be adjacent)
2) Replace a character in the string with any other lower case english letter. This operation costs $2$ $points$.
Help Gru in obtaining the lexicographically smallest string possible, by using at most $P$ points.

-----Input:-----
- First line will contain $T$, number of testcases. Then the testcases follow. 
- Each testcase contains two lines of input, first-line containing two integers $N$ , $P$.
- The second line contains a string $S$ consisting of $N$ characters.

-----Output:-----
For each testcase, output in a single containing the lexicographically smallest string obtained.

-----Constraints-----
- $1 \leq T \leq 10$
- $1 \leq N \leq 10^5$
- $0 \leq P \leq 2N$
- $S$ only consists of $'a'$ and $'b'$

-----Sample Input:-----
1
3 3
bba

-----Sample Output:-----
aab

-----Explanation:-----
We swap $S[0]$ and $S[2]$, to get $abb$. With the 2 remaining points, we replace $S[1]$ to obtain $aab$ which is the lexicographically smallest string possible for this case.

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

ns = {"__name__": "__main__"}
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'def __starting_point():\n t = int(input())\n for _ in range(t):\n  n, p = input().split()\n  n, p = int(n), int(p)\n  s = input()\n  a, b = 0, 0\n  arr = [0] * n\n  for i in range(n):\n   arr[i] = s[i]\n  for c in s:\n   if c == \'a\':\n    a += 1\n   else:\n    b += 1\n  swap = 0\n  for i in range(a):\n   if s[i] == \'b\':\n    swap += 1\n  tmpp = p\n  if p <= swap:\n   for i in range(n):\n    if p == 0:\n     break\n    if arr[i] == \'b\':\n     arr[i] = \'a\'\n     p -= 1\n   p = tmpp\n   for i in range(n - 1, -1, -1):\n    if p == 0:\n     break\n    if arr[i] == \'a\':\n     arr[i] = \'b\'\n     p -= 1\n   for c in arr:\n    print(c, end="")\n   print()\n  else:\n   for i in range(n):\n    if i < a:\n     arr[i] = \'a\'\n    else:\n     arr[i] = \'b\'\n   p -= swap\n   for i in range(n):\n    if arr[i] == \'b\':\n     if s[i] == \'b\' and p >= 2:\n      p -= 2\n      arr[i] = \'a\'\n     if s[i] == \'a\' and p >= 1:\n      p -= 1\n      arr[i] = \'a\'\n   for c in arr:\n    print(c, end="")\n   print()\n\n__starting_point()'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

```

Measured memory_bytes: 14227