After a heavy rainstorm, Barbara’s dog left muddy paw prints all over her back patio. She decided to rent an electric pressure washer to clean up the mess. The piecewise function below shows the rental charges for the pressure washer, dependent upon how many hours she rents it. Due to high demand, you cannot rent the washer for more than 24 hours at a time. Barbara’s brother asked to use the washer and agreed to pay Barbara for any additional monies owed. If Barbara used the washer for 3 hours and her brother returned it to the store 7 hours after she rented it, how much does her brother owe her?
$15.00
$41.00
$60.00
$61.00

Submarines control how much they float or sink in the ocean by changing the volume of air and water contained in large ballast tanks. when the tanks are completely full of water, the submarine increases its overall mass and sinks down to the bottom. when the tanks are completely full of air, the submarine reduces its overall mass and floats to the surface. depending on the density of the seawater surrounding the submarine, it will pump seawater in or out of the tanks in order to achieve the same overall density as the sea water and float neutrally in the water. the volume of the submarine never changes. when the tanks are completely full of water, a submarine with a volume of 7.8\times10^3\text{ m}^37.8×10 3 m 3 7, point, 8, times, 10, start superscript, 3, end superscript, space, m, start superscript, 3, end superscript has a total mass of 8\times10^6\text{ kg}8×10 6 kg8, times, 10, start superscript, 6, end superscript, space, k, g. the density of the seawater is 10^3\text{ kg/m}^310 3 kg/m 3 10, start superscript, 3, end superscript, space, k, g, slash, m, start superscript, 3, end superscript. to make that submarine float neutrally, and neither float nor sink in the ocean, what volume of water does that submarine need to subtract from its tanks?