A salesman gets commission on total sales at 9%. If the sale is exceeded Rs.10,000 he gets an additional commission as bonus of 3% on the excess of sales over Rs.10,000. If he gets total commission of Rs.1380, then the bonus he received is:

Commission up to 10000 =  $\frac{10000x9}{100}$ = 900 

Again after 10000, 

              Commission    :   Bonus 

                           9       :   3 

                         3x        :   x

 Therefore,   Bonus =  $1380-900\times \frac{1}{4} = Rs. 120$