Parse a receipt

A receipt is one string with one line per item, each line being <item> x <quantity> @ <price>. Write receipt_total(text) that returns the total cost. Lines may have extra spaces at the ends; blank lines are skipped.

receipt_total("bread x 3 @ 25\nmilk x 2 @ 2.5")  ->  80.0
receipt_total("")                                  ->  0

def receipt_total(text):
    ...