The situation can be drawn as 
The frictional force, f=μN=μmg[∵N=mg] From Free body diagram (FBD), the resultant force is ∣F∣=N2+f2=(mg)2+(μmg)2=mg1+μ2 This is the minimum force required to move the object. But as the body is not moving ∴∣F∣≤mg1−μ2