\(a,N_{mt}=N.\left(2^5-1\right)\\ \Leftrightarrow74400=N.31\\ \Leftrightarrow N=2400\left(Nu\right)\\ b,C=\dfrac{N}{20}=\dfrac{2400}{20}=120\left(vòng\right)\\ L=\dfrac{N}{2}.3,4=\dfrac{2400}{2}.3,4=4080\left(A^o\right)\\ c,rN_{mt}=3.2^5.\dfrac{N}{2}=96.\dfrac{2400}{2}=115200\left(ribonu\right)\)