Answer:
17.799°
Explanation:
When the bullet hits the block at that time the momentum is conserved
So, initial momentum = final momentum

So 

Now energy is also conserved
So 

Answer is: $637.28; just did the math but i really don’t want to type it all out.
Answer:
Numbers 4, 6, & 7 are correct
Explanation:
4- this allows the op amp to have zero voltage so that maximum voltage is transferred to output load.
6- this ensures that op amp doesn't cause loading in the original circuit, high input impedance would not deter the circuit from pulling current from it.
7- high difference between upper and lower frequencies.