Need help with relational algebra (must not use aggregate functions and grouping)

Questions:

1) Retrieve the names of authors who have written at least two books.

2) The quality of each book available at Henry Books branches is specified in the Copy Relation. If all possible qualities of a specific book are available at the Henry Books branches collectively, then output its title.

Relations and their Attributes are specified below with the identification of the Primary Key at the end of each Relation: a) Author - (authorNum/numeric, authorLast/char, authorFirst/char) PK: authorNum

b) Book - (bookCode/char, title/char, publisherCode/char, type/char, price/numeric, paperback/char) PK: bookCode

c) Branch - (branchNum/numeric, branchName/char, branchLocation/char, numEmployees/numeric) PK: branchNum

d) Inventory - (bookCode/char, branchNum/numeric, onHand/numeric) PK: bookCode

e) Publisher - (publisherCode/char, publisherName/char, city/char) PK: publisherCode

f) Wrote - (bookCode/char, authorNum/numeric, sequence/numeric) PK: bookCode,authorNum

Sequence refers to the sequence in which this author appears on the cover first author, second author, etc.

g) Copy - (bookCode/char, branchNum/numeric, copyNum/numeric, quality/char, price/numeric) PK: bookCode, branchNum, copyNum

Database: https://users.cs.fiu.edu/~navlakha/4710/Henry-Complete-modified.rdb