Minimum AVC occurs when MP=AP.
This occurs at 80 units of labor and 20000 units of output (AP x L = 20000). From this AVC = w / AP = 2 / 250 = .008
For part 4, at 100 units of labor, AP = 225 so Q = 22500 (225 x 100). You can calculate TVC = $2 x 100 units = 200, then calculate AVC = TVC / Q = 200 / 22500 = .0088