The total amount for a compound interest is given by the formula:
where P is the principal (the initial investment), r is the interest rate in decimal form, n is the number of times the amount is compounded in a given time t and t is the time of investment.
In this case the principal is $6000, the interest rate in decimal form is 0.078, since the amoun is compounded quarterly then n=4, and the time of investment is 19. Plugging this in the formula we have:
Therefore, the total amount after 19 years is $26,036.39