A wooden block with mass 0.26{\rm kg} rests on a horizontal table, connected to a string that hangs vertically over a friction-less pulley on the table's edge. From the other end of the string hangs a 0.20{\rm kg} mass.

What minimum coefficient of static friction \mu _{{\rm s}} between the block and table will keep the system at rest?

Find the block's acceleration if \mu _k =0.17.