Question 973186
To find the amount we use the formula A = P(1 + rt) where 

P is the Principal = $400

r is the interest rate 5.4% or 5.4/100 = 0.054 per year

and of course t is time = 1 year

Therefore, A = 400(1 + 0.054(1)) = $421.60

and this is the total amount he will have at the end of one year.