Can you please explain the equation you use, I am having trouble understanding which ones to use and why.

Problem 5: Betty and Bob are interested in borrowing money for 4 years as per compound interest. They have shopped around and have found the following plans: Plan 1: 8% per annum continuously compounded for the first year and 9% per annum continuously compounded for the next 3 years. Plans 2: 10% per annum continuously compounded for the first 18 months and 6% per annum compounded monthly for the remainder of the time. Plan 3: 9% per annum compounded semiannually for the first 9 months and 8% per annum compounded quarterly for the remainder of the time. Plan 4: 8% per compounding period of 8 months. This is to last for the entire 4 years. For each plan algebraically find the effective rate of interest per annum and the equivalent continuous rate of interest per annum. Rank the plans from Best to Worst for Betty and Bob. Your final numerical answers should be correct to 3 places after the decimal point