For each transaction below, calculate the amount of expense to be recorded in the current period using accrual$-$basis accounting:

Required:

a$.$ Paid $$4,200$ on account for supplies purchased last period. All supplies were used last month.

b$.$ Paid $$5,800$ cash for advertising in the current period.

c$.$ Employees worked in the current period but will not be paid until the following period, $$4,800.$