the length, breadth and height of a room is 8m, 6m and 4m respectively.there is one door of size 1 1/2m * 2 1/2m, two windows each of size 1/2m *1 1/4m and 8 ventilators each of size 0.3m * 0.5m, what is the cost of white washing on its four walls at the rate of rs. 5 per square metre