Calculating the Amount of an Annuity
An annuity is a series of equal payments made at regular intervals. In this case, we are given the annuity amount of 150 to be paid for 12 years at a compound interest rate of 3.5% per annum. To calculate the total amount of the annuity, we need to consider the compound interest formula.

Compound Interest Formula
The compound interest formula is given by:
A = P(1 + r/n)^(nt)
where:
A = the future value of the investment/loan, including interest
P = the principal investment amount (initial payment)
r = annual interest rate (in decimal form)
n = number of times that interest is compounded per year
t = number of years the money is invested/borrowed for

Calculating the Future Value of the Annuity
In this case, the annuity amount is 150, the annual interest rate is 3.5% (0.035 in decimal form), the number of compounding periods per year is 1, and the number of years is 12. Plugging these values into the compound interest formula, we get:
A = 150(1 + 0.035/1)^(1*12)
A = 150(1 + 0.035)^12
A = 150(1.035)^12
A = 150(1.469331)
A = 220.40
Therefore, the total amount of the annuity after 12 years at a compound interest rate of 3.5% per annum would be 220.40.