Answer:
Dale would reach his goal with an annual interest rate of 6.18%.
Explanation:
For compounding continuously, recall the following equation:

A = final amount ($4200)
P = principal amount ($2000)
r = rate (unknown)
t = time (12 years).
You'll have to use natural logs for these types of questions. Remember that ln (e) = 1.
See the work done in the attached file.
Hope this helps!