The following code attempts to implement the optimal car pooling solution. Which line contains a subtle bug that can cause incorrect capacity checks?

The following code attempts to implement the optimal car pooling solution. Which line contains a subtle bug that can cause incorrect capacity checks?

def carPooling(trips, capacity):
    max_location = 0
    for _, start, end in trips:
        max_location = max(max_location, end)
    diff = [0] * (max_location + 1)
    for num, start, end in trips:
        diff[start] += num
        diff[end] += num  # Bug here
    current_passengers = 0
    for i in range(max_location + 1):
        current_passengers += diff[i]
        if current_passengers > capacity:
            return false
    return true