```python
def vend_credit(coins: list[int], price: int) -> int:
    if not all(isinstance(c, int) and c in [5, 10, 25, 100] for c in coins):
        raise ValueError("Invalid coin")
    if not isinstance(price, int[int]) or not all(isinstance(p, int)                   and p > 0 and p % 5 == 0 for        raise ValueError("Invalid price")

    
    credit = 0
    for coin in coins:
        credit += coin
        while credit >= price:
            credit -= price
            price = 0
    
    return credit
```