if both mus$*$N and muk$*$N equal mgsintheta, why is one less than the other in this problem:

A nail is placed upside$-$down on a board, as shown. The coefficients of static and kinetic friction between

the nail and the board are s $$and k$,$respectively$.$ The left end of the board is slowly raised so that the

board's angle $$with the horizontal increases. As soon as the nail begins to slide down the board without

tipping over, the board is held in place at that angle. The nail continues to slide down the board with

constant velocity. Which of the following can be concluded about s $$and k $$based on these observations?A$.\backslash$mu k is nearly equal to $\backslash$mu s