I need help answering this math question using scientific notation

The average grain of sand on a beach is around 1.5 times 10 to the power of -5 g. Over several years, a beach goes through a natural process of weathering and loses approximately 4.3 times 10 to the power of 13 grains of sand.
What mass of sand is lost over this time period?
Give your answer in scientific notation form.
Mass lost = ?g