[单选题]
In the Atwood machine shown in Fig. 4-1, if Mrrd-2 b +1ewc+hn6kb (jmpx4 i = 0.60 kg ayz w9+:tm2re g.igs1 fnd m = 0.40 kg, what is the magnitude of the acceleration of the system? (Ignore friction and the mass of the pulleyi+:e ry2w fmz st1.g9g.)
A. $5.3 \; m/s^2$
B. $3.9 \; m/s^2$
C. $2.0 \; m/s^2$
D. $0.98 \; m/s^2$
