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: how many integerskgreater than 100 and less than 1100 are there such that if the hundreds and the units digits ofkare reversed , the resulting integer is k + 99 ? 
Options: a ) 50 , b ) 60 , c ) 70 , d ) 80 , e ) 90
e

Problem: if 1 / 12 of the passengers on a ship are from north america , 1 / 4 are europeans , 2 / 9 are from africa , 1 / 6 are from asia and the remaining 50 people are citizens of other continents , then how many passengers are on board the ship ? 
Options: a ) 120 , b ) 140 , c ) 150 , d ) 160 , e ) 180
e

Problem: when positive integer n is divided by 3 , the remainder is 1 . when n is divided by 7 , the remainder is 5 . what is the smallest positive integer k such that k + n is a multiple of 21 ? 
Options: a ) 2 , b ) 4 , c ) 6 , d ) 8 , e ) 10

a