ONLY SOLVE THE THIRD QUESTION

The diagram shows the surface of a garden pond, made from a rectangleand two semicircles. The rectangle measures 3 m by 1.2 m.

(a) Calculate the area of this surface.
4.73 m^2

(b) The pond is a prism and the water in the pond has a depth of 20 cm. Calculate the number of litres of water in the pond.
946 litres

(c) After a rainfall, the number of litres of water in the pond is 1007. Calculate the increase in the depth of water in the pond. Give your answer in centimetres.
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I solved the first and the second questions. Please solve the third question.