Apopulation of butterflies decreases exponentially at a rate of 18.3% per year. what is the equivalent monthly rate to the nearest hundredth of a percent? 1.27% 1.41% 1.53% 1.67%

The population of butterflies decreases exponentially at a rate of 18.3% per year which equal to 18.3%  per 12 month. The exponent function will look like:
an=a0(1+r)^t

If you want to convert year into the month, it is like convert t into 12 t. The calculation would be:
a0(1+r1)^t = a0(1+r2)^12t
(1-0.183)^1 = (1+r2)^12
(0.817) = (1+r2)^12
 = (1+r2)^(12/12)
1+r2= 0.983298
r2= 0.98329-1= 0.01671= 1.67%

Ithink its 126 hope its