View Compilation Error

0_0_36492077_13543.cpp: In function 'int main()':
0_0_36492077_13543.cpp:24:19: error: 'a' was not declared in this scope
         if(avg*n<=a&&avg*n>=b)
                   ^
0_0_36492077_13543.cpp:24:29: error: 'b' was not declared in this scope
         if(avg*n<=a&&avg*n>=b)
                             ^