Please workout on the answer. I am new to accounting and hence, I would appreciate if you could give details on the answer.

The following is a summary of the petty cash transactions for a week.

Income	$		Expenditure	$
Opening balance	500		Travelling expenses	150
Sale of stamps	10		Subsistence expenses	250
Sale of paper	50

Petty cash is maintained using the imprest system.

What sum should be reclaimed by the cashier at the end of the week?