What is the minimum coefficient of static friction needed

A man wants to push a package of shingles of total mass 35 kg up a roof being built at an angle of 35° to the horizontal. The coefficient of kinetic friction between the package and the roofing paper already in place is 0.31. How much force does the man have to exert on the package directly along the slope of the roof to cause the package to accelerate at 0.1 m/s2?
What is the minimum coefficient of static friction needed so that the package will not slide when it is left at rest on the roof?

Hello

the friction force is
Ff = mgcos(angle)*μ = 35*9.81*cos(35)*0.31 = 87.19 N
the gravitational force down the incline is
Fg = mgsin(angle) = 35*9.81*sin35 = 196.93 N
the net force necessary to accelerate the mass at 0.1 m/s^2 is
Fnet = ma = 35*0.1 = 3.5 N

And net force = total force - friction force - gravitational force
3.5 = total force - 87.19 - 196.93
total force = 287.6 N <--- ans.
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to stay at rest, friction force = gravitational force at least.
35*9.81*cos(35)*μ = 35*9.81*sin(35)
μ = cos(35)/sin(35)
μ = 0.7 at least <--- ans.

Regards