The formula for the amount A in an account with principal P and interest rate r compounded annually for t years is
... A(t) = P(1+r)^t
You want to find A when P=400, r=0.05, and t=3. Substituting those values gives you
... A(3) = 400·(1 +0.05)³
The appropriate choice is
... A. A(3) = 400·(1 +0.05)³