Explanation

The bookseller sold the book for Rs.60 to make a profit of 20%. This means that the selling price (Rs.60) is 120% of the cost price (100% + 20% profit).

To find the cost price, we can set up an equation:

Selling Price = Cost Price + Profit

60 = Cost Price + (20% of Cost Price)

Let's convert the percentage to a decimal and simplify:

60 = Cost Price + 0.20(Cost Price)

60 = 1.20(Cost Price)

Now, divide both sides by 1.20:

Cost Price = 60 / 1.20

Cost Price = 50

So, the cost price of the book is Rs.50.

To earn a profit of 10%, the bookseller should have sold the book for:

Selling Price = Cost Price + Profit

= 50 + (10% of 50)

= 50 + 5

= 55

Therefore, the correct answer is: 55