def cost_fun(x_list, y_list, w, b):

    m = len(x_list)
    total_err = 0

    for i in range(m):
        pred = w * x_list[i] + b
        err = pred - y_list[i]
        total_err += err ** 2

    return total_err / (2 * m)


distances = [1, 2, 3, 4, 5]
actual_times = [12, 17, 22, 27, 32]

wrong_guess = cost_fun(distances, actual_times, w=4, b=10)
correct_guess = cost_fun(distances, actual_times, w=5, b=7)

print("Cost for w=4, b=10:", wrong_guess)
print("Cost for w=5, b=7:", correct_guess)

# Cost for w=4, b=10: 1.0
# Cost for w=5, b=7: 0.0

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