Question 1028614
{{{A=P(1+r/n)^(nt)}}}
{{{A = 400(1+(0.08)/(1))^((1)(4))}}}
The (1) is the number of compounding periods per year
The (4) is the number of years.
{{{A = 400(1+0.08)^4}}}
{{{A = 544.20}}}
The amount of interest is 544.20 - 400 = $144.20
Now determine the amount after a total of 8 years
{{{A = 400(1+0.08)^8}}}
New amount = 740.37
So between the end of year 4 and year 8 
the increase is 740.37 - 544.20 = $196.17