Sanderson is a bus driver who earns a monthly gross income of $3,500. His wife Norma is the manager of an automotive parts store and she earns gross income of $2,250 every two weeks. The couple has living expenses, including their mortgage and property tax, of $3,000 a month. They have other debt payments totalling $900 per month and they invest $900 a month to their registered retirement savings plans (RRSPs) and tax-free savings accounts (TFSAs). Their remaining monthly discretionary expenses total $1,200 per month. Sanderson has an average tax rate of 20% and Normas is 25%. What is the couples monthly cash flow?
a)		-$1,512
b)		$456
c)		$1,356
d)		$1,656