please solve the Q fast ..thanks

Alice want to send a 4GB file to Bob. Alice want to keep the file confidential. She also want to make sure no other persons could modify the message. Alice does not share any secret key with Bob. However, Alice and Bob know each other's public key. Assume Alice's private key is PRA, and her public key is PUA. Similarly, Bob's private key is PRg, and his public key is PUB. 1. Sketch a diagram to illustrate how Alice should do this? 2. Sketch a diagram to explain how Bob should process the message received from Alice