Iguessed it prob not right but the question is how much money does darius have at the end of the first 6 months including interest

Use the compound interest formula

A = P (1 + r/n)^(nt).

Here A = unknown; B = initial amount = $300;
r = rate = 0.0218; n = 2 (2 compounding periods per year); and t = 1/2 (year).

Then A = $300 (1+0.0218/2)^(2*[1/2])
           A = $300 (1.0218)^1         or       A = $300(1.0218)   =   $306.54