Force on m by 2m such that m is stationary on M

[Cali37]

Homework Statement

A mass m1 is placed upon a second mass M on a horizontal surface. A massless string connects mass m1 to mass m2. If the coefficient of static friction between M and the horizontal surface is μs, answer the following:
a) There is a coefficient of static friction μs between M and m1 such that m1 will remain stationary on M. Prove or disprove.
b) If the masses are now interchanged such that m1 is switched with m2, then the answer to part (a) remains the same. Prove or disprove.

Homework Equations

m1+M=m2
ƩFx=F-T
ƩFy=N-mg

The Attempt at a Solution

N=mg

 

[haruspex]

Please supply the rest of the information. There's obviously some missing.

 

[Cali37]

Thats all that my teacher gave me, you can see why I am struggling. Thanks anyway :)