Answer:
2.2%
Explanation:
Given the initial invested as £3550, compound interest rate for first two years as 2.6% and interest for third year as R% and a final amount as £3819.21, R% can be calculated as:
#Compound interest in first two years:

#Hence, the total amount after first two years is £3737. To find R%, we further compound it for the final year and equate it to the final amount:

Hence, R% is equivalent to 2.2%