Write RA expressions to express the following questions over the schemas in Question $1.$

$1.$ What PC models have a speed of at least $4\mathrm{.}5?$

$2.$ Find the model number and price of all products made by manufacturer B$.$

$3.$ Which manufacturers make laptops with a hard disk of at least $100$GB$?$

$4.$ Find the model numbers of all color laser printers.

$5.$ Find manufacturers that sell Laptops but not PC$$s$.$

$*$ Find pairs of PC models that have both the same speed and RAM. List each pair once; e$.$g$.,($i$,$j$)$

but not $($j$,$ i$).$

$*$ Find the manufacturer$($s$)$ of laptops with the highest speed.