To find the original amount invested, use the formula for simple interest, which is A = P(1 + rt), where A is the total amount, P is the principal, r is the rate, and t is the time in years. Given that the total amount after 4 years is N330.00 and the interest rate is 8% (0.08), we can rearrange the formula to solve for P. Substituting the known values leads to P = 330 / (1 + 0.08 * 4), resulting in an original investment of N250.00.