Fath Co$.$ owns $100\%$ of Son, Inc. On January $2,$ year $1,$ Fath sold equipment with an original cost of $$80,000$ and a carrying amount of $$48,000$ to Son for $$72,000.$ Fath had been depreciating the equipment over a five$-$year period using straight line depreciation with no residual value. Son is using straight line depreciation over $3$ years with no residual value. In Fath's December $31,$ year $1,$ consolidating worksheet, by what amount should depreciation expense be decreased?