Answer:
During the first year he had an annual interest of 12%, and in the second year of 25%
Explanation:
To calculate the interest of the first year:
(Initial capital of the first year / final capital of the first year) - 1 = interest of the first year
(300/336) - 1 = 0.12 = 12%
To calculate the interest of the second year:
(Initial capital of the secondyear / final capital of the second year) - 1 = interest of the second year
(336/420) - 1 = 0.25 = 25%