4.1 Calculate the internal dimensions of the trough in centimetres. (3) 4.2 Hence, show by calculations that the internal volume (capacity) of the trough is 8.091 000 cm³. (2) You may use the formula: Volume 1xwxh 4.3 Given that 1 gallon of paint covers approximately 280 000 cm². Mr. Masondo claimed that 3 litres of paint will be enough to paint the internal surface of the trough. Verify, using calculations if his claim is correct. (6) You may use the formula: Surface area of a rectangle = (1 × w) +2(1xh) +2(wxh) NOTE: 1 gallon = 3,7850 8 [11]​