1 - 500 principal earning 4% compounded quarterly, after 6 year.

A - 1.281.65

B - 634.87

C - 709.26

D - 632.66

2 - 3500 deposit earning 6.75% compounded monthly, after 6 months.

A - 3,619.80

B - 3,743.70

C - 3,748.22

D - 4,860.36

You'll have $634.87 after 6 years at 4% compounded quarterly, thus B:

You'll have $3,619.80 after 6 months at 6.75% compounded monthly, thus A:

Formulas where n = 1 (compounded once per period or unit t)

1. Calculate Accrued Amount (Principal + Interest) A = P (1 + r) ^t

2. Calculate Principal Amount, solve for P. P = A / (1 + r) ^t

4. Calculate the rate of interest in decimal, solve for r. r = (A/P) 1 / (^t - 1)

5. Calculate rate of interest in percent ... Calculate time, solve for t.