View Compilation Error

0_0_8394283_12817.c:7: error: syntax error before '/' token
0_0_8394283_12817.c: In function `sum':
0_0_8394283_12817.c:17: error: `index_c' undeclared (first use in this function)
0_0_8394283_12817.c:17: error: (Each undeclared identifier is reported only once
0_0_8394283_12817.c:17: error: for each function it appears in.)
0_0_8394283_12817.c: In function `main':
0_0_8394283_12817.c:48: error: `index_c' undeclared (first use in this function)