I need help with these two questions and please write in detail the answer and neat for me to understand.Thank you.

I need help with these two Questions Please. Please write in detail the answer and neat for me to understand. Thank you. Find grammars for I- fa, bl that generate the sets of: 1. all strings that start with at least 3 a's (2 points) 2. all strings that start with a and end with b (3 points) 2) Find a grammar for the language L = an, where n is even