A crate of mass m is connected to a stone weighing 5.0 kg through a massless string and a frictionless pulley as shown in the figure. Determine the value of 'm' that will keep the system moving at a constant speed if μ_k = 0.18 and μ_s = 0.42 are the coefficients of friction between the crate and the surface.

• A. 8.0 kg
• B. 12 kg
• C. 28 kg
• D. 39 kg

Answer: (C)