A $0\mathrm{.}75-$kg block slides on a rough horizontal tabletop. Just before it hits a horizontal ideal spring, its speed is $3\mathrm{.}5$ m$/$s$.$ It compresses the spring $5\mathrm{.}7$ cm before coming to rest. If the spring constant is $1200$ N$/$m$,$ the thermal energy of the block and the tabletop must have:

not changed

decreased by $1\mathrm{.}9$ J

decreased by $2\mathrm{.}6$ J

increased by $1\mathrm{.}9$ J

increased by $2\mathrm{.}6$ J