View Compilation Error

0_0_1731623_7121.cpp: In function `double Solve()':
0_0_1731623_7121.cpp:65: error: `c' undeclared (first use this function)
0_0_1731623_7121.cpp:65: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1731623_7121.cpp:65: error: expected `;' at end of input
0_0_1731623_7121.cpp:65: error: expected `}' at end of input