In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: find the principle on a certain sum of money at 5 % per annum for 3 1 / 5 years if the amount being rs . 580 ? 
Options: a ) rs . 500 , b ) rs . 5100 , c ) rs . 530 , d ) rs . 540 , e ) none of these
a

Problem: two numbers are less than a third number by 40 % and 47 % respectively . how much per cent is the second number less than the first ? 
Options: a ) 95 % , b ) 88 % , c ) 85 % , d ) 90 % , e ) none of these
b

Problem: the average age of 39 students in a group is 14 years . when teacher ' s age is included to it , the average increases by one . what is the teacher ' s age in years ? 
Options: a ) 35 years , b ) 45 years , c ) 51 years , d ) 54 years , e ) none of these

d