A wooden bookshelf has external dimensions as follows: Height = 10 cm, Depth = 25cm, Breadth = 85 cm (See in Figure). The thickness of the plank is 5 cm everywhere. The external faces are to be polished and the inner faces are to be painted. If the rate of polishing is 20 paise per `c m^2` and the rate of painting is 10 paise per `c m^2` . Find the total expenses required for polishing and painting the surface of the bookshelf.

Explanation

To solve the problem of calculating the total expenses required for polishing and painting the surface of the bookshelf, we will follow these steps:

### Step 1: Determine the external dimensions of the bookshelf.
- Height (H) = 110 cm
- Depth (D) = 25 cm
- Breadth (B) = 85 cm

### Step 2: Calculate the internal dimensions of the bookshelf.
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