Definition: In this task, you need to answer the given multiple-choice question on geometry. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Input: Problem: the radius of a cylinder is 12 m , height 21 m . the lateral surface area of the cylinder is : 
Options: ['a ) 1584', 'b ) 1854', 'c ) 1458', 'd ) 1485', 'e ) none of them']
Output:
a