On January 1, 2013, Terps Company purchased a new machine for $30,000. The estimated useful life was 10 years with an estimated residual value of $6,000. Straight-line depreciation is used and is computed to the nearest month. On July 1, 2020, the machine was sold for $9,000 cash. The gain (loss) on disposal was ________.

$1,200 gain

$1,000 gain

$3,000 loss

$1,800 gain