From the following particulars, prepare a statement showing (a) prime cost, (b) works cost, (c) cost of production and (d) cost of sales:

Rs

Opening stock of finished goods

9,750

Closing stock of finished goods

11,100

Raw materials purchased

35,250

Carriage on materials purchased

850

Direct wages

18,450

Factory expenses

2,750

Selling expenses

2,450

Office cost

1,850

Sales

75,000

Sales of scrap

250

Also show by what percentage the average selling price in the aforementioned case should be increased in order to double the net profit.