Stopping distance and static friction

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Homework Statement

A large box of mass M is moving on a horizontal surface at speed v_0. A small box of mass m sits on top of the large box. The coefficients of static and kinetic friction between the two boxes are μs and μk, respectively.
Find an expression for the shortest distance dmin in which the large box can stop without the small box slipping.
Express your answer in terms of the variables v0, μs, and appropriate constants.

Homework Equations

F=μN
a=F/m

delta S = -v_i^2 / (2a_s)= -v_0^2 / 2a_s

The Attempt at a Solution

Question asks for minimum stopping distance, delta s, I am looking for the max deceleration that won't have greater force than the force due to static friction, μN.

dmin = -v_0^2 / 2(u_s/m)
Is this correct?
thanks for any help

 

[mfb]

Do the units match?
Without matching units it cannot be right.