View Compilation Error

0_0_15113669_22216.cpp: In function 'int main(int, char**)':
0_0_15113669_22216.cpp:6:11: error: expected unqualified-id before ';' token
  double a,;
           ^
0_0_15113669_22216.cpp:9:3: error: 'b' was not declared in this scope
   b=4*a*a*a*3.14/3;
   ^