Consider the relational database schema of Exercise $3.$

Supplier$($supplier$-$id$,$ name, city$)$

Store $($store$-$id$,$ sname, city$)$

Product$($barcode$,$ pname, price, itsshoes, itsabag, color,

supplier$-$id$)$

Has$\_$stock$($store$-$id$,$ barcode, quantity$)$

Express in tuple relational calculus algebra the following queries:

A$.(3\%)$ Find the products that have price above $40($e$.$g$.$ CAD$).$

B$.(5\%)$ Find the barcode$($s$)$ of all products that have price above $40($e$.$g$.$ CAD$).$

C$.(7\%)$ Find the barcode$($s$)$ of the products that are sold in the store with store$-$id equal to $\text{'}1\text{'}$ but not

in the store with store$-$id equal to $\text{'}2\text{'}.$

D$.(10\%)$ Find the barcode$($s$)$ of all the products that are sold in all the stores in the city of 'Ottawa'.