How long will it take for an investment of 4300 to double if

How long will it take for an investment of $4,300 to double if interest is 3.1% compounded continuously.

Compound Interest:

Amount = Principal{ 1+ rate/100)^ time

Principal = $ 4,300

Amount = 2x 4300 = $ 8600

8600 = 4300{ 1+ 3.1/100)^t

2 =1.031^t

Taking natural log on both sides:

ln2 = t*ln(1.031)

t = ln2/ln1.031 = 22.7 years it takes to double the investment