We would apply the formula for determining compound interest which is expressed as
A = P(1 + r/n)^nt
Where
A = total amount in the account at the end of t years
r represents the interest rate
n represents the periodic interval at which it was compounded
P represents the initial amount deposited
From the information given,
P = 4200
r = 3.5/100 = 0.035
n = 1 because it was compounded once in a year
t = 7
By substituting these values into the equation,
A = 4200(1 + 0.035/1)^1 * 7
A = 4200(1.035)^7
A = 5343.57
The answer is $5343.57