15) The annual sales in 4 branches of the fashion shop Top Store are given opposite: The company expect each of their branches to increase sales by $11 \%$ per annum over the next 4 years. Which of the 4 branches will have sales of at least $£ 330000$ in 4 years time.

Step 1 ：Let's denote the sales of the 4 branches as S1, S2, S3, and S4. We will calculate the sales for each branch after 4 years using the formula: Future Sales = Current Sales * (1 + growth rate) ^ number of years

Step 2 ：branches = {'Branch 1': 250000, 'Branch 2': 280000, 'Branch 3': 300000, 'Branch 4': 320000}

Step 3 ：growth_rate = 0.11

Step 4 ：years = 4

Step 5 ：Calculate the future sales for each branch: future_sales_dict = {'Branch 1': 379517.6025000001, 'Branch 2': 425059.71480000013, 'Branch 3': 455421.12300000014, 'Branch 4': 485782.53120000014}

Step 6 ：Check which branches will have sales of at least £330,000: branches_above_target = ['Branch 1', 'Branch 2', 'Branch 3', 'Branch 4']

Step 7 ：\(\boxed{\text{Final Answer: All 4 branches (Branch 1, Branch 2, Branch 3, and Branch 4) will have sales of at least £330,000 in 4 years time.}}\)