P = $1986 the principal

r = 0.04 or 4% annual interest rate

m = 1 compounding period per year (compounded semiannually)

i = r/m = 0.04/1 = 0.04 interest rate per period

t = 23 years

n = t*m = 23*1 = 23 total number of compounding periods

A = the future value (the amount in the account after 23 years)

A = P(1 + i)^n

A = 1986(1 + 0.04)^23
........
click here to see all the equation solution steps
........
A = $6,444.17

The interest is I = A - P:

I = $6,444.17 - $1,986

I = $4,458.17

The interest will be $4,458.17.