Answer
(a) 120 gallons
(b) 420 gallons
(c) 2076 gallons
Work Step by Step
(a) There are 30 minutes in half an hour, thus saving $120$ gallons of water during that time period.
(b) The water supply is given by the area under the graph, which is$\frac{(4+10).60}{2}=420$ gallons.
(c) The water supply is given by the area under the graph and therefore by:
$\int_{0}^{120}(\sqrt{t}+10) d t=\left.\left(\frac{2}{3} t^{3 / 2}+10t\right)\right|_{0} ^{120}=\frac{2}{3}(120)^{3 / 2}+1200$
$=160 \sqrt{30}+1200 \approx 2076$ gallons
