d
(d) Limiting friction \( = {\mu _s}R = {\mu _s}mg = 0.5 \times 60 \times 10 = 300\;N\)

Kinetic friction \( = {\mu _k}R = {\mu _k}mg = 0.4 \times 60 \times 10 = 240\;N\)

Force applied on the body \(= 300 \,N\) and if the body is moving then,

Net accelerating force = Applied force -Kinetic friction

\(⇒ ma = 300 - 240 = 60\)

\(\therefore a = \frac{{60}}{{60}} = 1\;m/{s^2}\)