Answer:
410.32
Step-by-step explanation:
Given that the initial quantity, Q= 6200
Decay rate, r = 5.5% per month
So, the value of quantity after 1 month, 

The value of quantity after 2 months, 

From equation (i)

The value of quantity after 3 months, 

From equation (ii)


Similarly, the value of quantity after n months,

As 4 years = 48 months, so puttion n=48 to get the value of quantity after 4 years, we have,

Putting Q=6200 and r=5.5%=0.055, we have

Hence, the value of quantity after 4 years is 410.32.