Answer
We can make an energy statement for the system:
$W = 140~J$
$\Delta K = 130~J$
$\Delta U_g = -20~J$
$E_{th} = 30~J$
Work Step by Step
The person's work on the system is 200 J. Since the system does work of 60 J on the block, then the block does work of -60 J on the system.
We can find the work done on the system:
$W = 200~J-60~J = 140~J$
$\Delta K = 130~J$
$\Delta U_g = -20~J$
We can find $E_{th}$:
$W = \Delta K + \Delta U_g + E_{th}$
$E_{th} = W - \Delta K - \Delta U_g$
$E_{th} = 140~J - 130~J - (-20~J)$
$E_{th} = 30~J$
We can make an energy statement for the system:
$W = 140~J$
$\Delta K = 130~J$
$\Delta U_g = -20~J$
$E_{th} = 30~J$
