<p>Keep getting this error message when trying to compile inmain1.cpp. Need help figuring out how to make it compile. Thank youfor your time.</p><p><strong>Error Message:</strong></p><p>main.cpp:(.text+0x13): undefined reference to`circle::circle()'</p><p>main.cpp:(.text+0x32): undefined reference to`circle::circle(double)'</p><p>main.cpp:(.text+0x3e):