Pandas DataFrame で各州内のオフィスごとの売上高の割合を計算するにはどうすればよいですか?

import pandas as pd

# Create the DataFrame
df = pd.DataFrame({'state': ['CA', 'WA', 'CO', 'AZ'] * 3,
                   'office_id': list(range(1, 7)) * 2,
                   'sales': [np.random.randint(100000, 999999)
                             for _ in range(12)]})

# Calculate the sum of sales for each state
total_sales_by_state = df.groupby('state')['sales'].transform('sum')

# Calculate the percentage of sales for each office
df['sales_percent'] = 100 * df['sales'] / total_sales_by_state