Step 1 : 

The function is .

Apply partial derivative on each side with respect to .

.

Step 2:

The function is .

Apply partial derivative on each side with respect to .

.

.

The function is .

Find .

From part (b):

Apply partial derivative on each side with respect to .

Apply formula: .

.

The function is .

Find .

From part (b): .

Apply partial derivative on each side with respect to .

Apply formula: .

.