Linker output for Image/Shapes lab

// Linker output:

Point.o: In function `Point::Point()':
Point.cpp:(.text+0xd): undefined reference to `Shape::Shape()'
Point.o: In function `Point::Point(int, Matrix const&)':
Point.cpp:(.text+0x37): undefined reference to `Shape::Shape(int, Matrix const&)'
Point.o: In function `Point::Point(Point const&)':
Point.cpp:(.text+0x67): undefined reference to `Shape::Shape(int, Matrix const&)'
Point.o: In function `Point::~Point()':
Point.cpp:(.text+0x8c): undefined reference to `Shape::~Shape()'
Point.o: In function `Point::operator=(Point const&)':
Point.cpp:(.text+0xd6): undefined reference to `Shape::getColor() const'
Point.cpp:(.text+0xf0): undefined reference to `Shape::getOrigin() const'
Point.o:(.rodata._ZTV5Point[vtable for Point]+0x20): undefined reference to `Shape::operator<<(std::basic_ostream<char, std::char_traits<char> >&) const'
Point.o:(.rodata._ZTV5Point[vtable for Point]+0x24): undefined reference to `Shape::operator>>(std::basic_istream<char, std::char_traits<char> >&)'
Point.o:(.rodata._ZTV5Point[vtable for Point]+0x28): undefined reference to `Shape::operator=(Shape const&)'
Point.o:(.rodata._ZTI5Point[typeinfo for Point]+0x8): undefined reference to `typeinfo for Shape'