\(A_1=\dfrac{15\%N}{2}=180\left(nu\right)\)
\(T_1=\dfrac{30\%N}{2}=360\left(nu\right)\)
\(\rightarrow A=T=A_1+T_1=540\left(nu\right)\)
\(G_1=\dfrac{30\%N}{2}=360\left(nu\right)\)
\(C_1=\dfrac{25\%N}{2}=300\left(nu\right)\)
\(\rightarrow G=C=G_1+C_1=660\left(nu\right)\)