Частная производная 1ый курс

Решите задачу:

$U=U(v.w)\; \; ,\; \; v=v(c,d)\; ,\; \; w=w(c,d)\\\\U'_{d}=U'_{v}\cdot v'_{d}+U'_{w}\cdot w'_{d}\\\\ili\; \; \; \; \frac{\partial U}{\partial d}=\frac{\partial U}{\partial v}\cdot \frac{\partial v}{\partial d}+\frac{\partial U}{\partial w}\cdot \frac{\partial w}{\partial d} \\\\\\P.S.\; \; \; \; U'_{c}=U'_{v}\cdot v'_{c}+U'_{w}\cdot w'_{c}$