Given the task definition and input, reply with output. 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: in an election between two candidates a and b , the number of valid votes received by a exceeds those received by b by 15 % of the total number of votes polled . if 20 % of the votes polled were invalid and a total of 5720 votes were polled , then how many valid votes did b get ?
Options: a ) 1859 , b ) 2999 , c ) 2834 , d ) 2777 , e ) 2991
a