A machine costing $80,000$ has a useful life of $5$ years. The company's management estimates production for each year of the useful life as follows: $1$st year $1,000$ units, $2$nd year $1,200$ units, $3$rd year $1,200$ units, $4$th year $900$ units, and $5$th year $700$ units.

It is requested to calculate the depreciation for the $2$nd year using i$)$ the constant method and ii$)$ the units produced method