Finding the final amount in a word problem on continuous exponential growth or decay

Given:
The mass of radioactive follows an exponential decay model
The initial mass = 418 kg
Decreases at a rate = r = 4% per day
So, the general formula for the mass will be:
[tex]m=418\cdot(1-0.04)^d[/tex]where: (m) is the mass after (d) days
So, to find the mass after 2 days, we will substitute with d = 2
so,
[tex]m=418\cdot(1-0.04)^2=418\cdot0.96^2=385.2288[/tex]rounding to the nearest tenth
so, the answer will be mass after 2 days = 385.2 kg