Want to see if I'm doing this question right and the calculations are also correct. I have done this question three times now and keep getting different answers

Question

The formula is f(t) = P(1 + r/n)^nt 

$62,000 is invested in a CD with the interest rate of 25%

Time in years is 18

the compounding periods  per year is quarterly

and then they ask to do it again but with the compounding periods per year is semi-annually

They want all work shown thank you

Answer 1

f(t) = P(1 + r/n)nt where n is amount of periods within a year

P=$62,000; r=0.25; t=18; n=4 (for quarterly) or n=2 (for semi-annually)

f(18) = 62,000 * (1 + 0.25/4) ^ (4*18) where n=4 (quarterly)

f(18) = 62,000 * (1 + 0.25/2) ^ (2*18) where n=2 (semi-annually)

 

Answer 2

ƒ(t) = 62,000(1 + 0.25/4)^4*18 = 62,000(1.0625)⁷² = 62,000 * 78.6473 = $ 4,876,130.02
ƒ(t) = 62,000(1 + 0.25/2)^2*18 = 62,000(1.125)³⁶ = 62,000 * 69.421 = $ 4,304,101.43

Answer 3

If cauterly compounded investment then r/n = 0.25/4 = 0.0625 each quarter. 

The exponent nt = 4x18 = 72 quarters. Thus, if P = 62,000,

           f(t) = 62,000x(1.0625)⁷² =4,876,130

For semiannual compounding r/n = .25/2 = 0.125  and nt = 2x18 = 36

Now you can finish.