SUSL has a few $3$D printing equipment. SUSL is expected to batch depreciate these equipment for $$600/$month$.$ What would be the correct adjusting journal entry for end of January to record the depreciation? Please assume that last year's depreciation were properly recorded.

a$.$ debit equipment for $$600,$ credit depreciation for $$600.$

b$.$ Debit depreciation expense for $$600,$ credit accumulated depreciation for $$600.$

c$.$ Debit depreciation expense for $$600,$ credit equipment for $$600.$

d$.$ Debit accumulated depreciation for $$600,$ credit depreciation for $$600.$