Please provide answers to the following three exercises/questions. Please provide a natural deduction proof for the following valid, deductive...

Please provide answers to the following three exercises/questions.

1. Please provide a natural deduction proof for the following valid, deductive argument:

Premise 1: ~ ( F & A )

Premise 2: ~ ( L v ~ A )

Premise 3: D > ( F v L )       / ~ D

2. Answer the following question: can one prove invalidity with the natural deduction proof method? Why or why not?