$.$ Assume an older truck with a cost of $$18,000$ has accumulated depreciation of $$10,000.$ The older truck and $$21,000$ cash are traded for new equipment valued at $$30,000.$ Which of the following would be part of the journal entry to record this exchange?

a$.$ debit Gain on Disposal for $$1,000$

b$.$ credit Accumulated Depreciation, Truck for $$10,000$

c$.$ credit Gain on Disposal for $$2,000$

d$.$ debit Equipment for $$30,000$