Yes, calculate the average monthly rate of return first, because it is calculated by compound interest, and the average monthly rate of return X is: (1+x) 12-1 = .821, x = .6597, that is, the monthly interest rate is .6597%

After 1,15 years (18 months) a month, The final income calculation formula is as follows: 1 * [(1+.6597%)+(1+.6597%) 2+(1+.6597%) 3+...+(1+.6597%) 18]

After simplification, it is: