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: if a person walks at 20 km / hr instead of 10 km / hr , he would have walked 20 km more . the actual distance traveled by him is :
Options: a ) 20 km , b ) 56 km , c ) 60 km , d ) 70 km , e ) 80 km
a

Problem: a retailer bought a hat at wholesale and marked it up 60 % to its initial price of $ 24 . by how many more dollars does he need to increase the price to achieve a 100 % markup ?
Options: a ) 3 , b ) 4 , c ) 5 , d ) 6 , e ) 7
d

Problem: simplify : 896 x 896 - 204 x 204
Options: a ) 761200 , b ) 761400 , c ) 761800 , d ) 761500 , e ) none of them
a