Platinum $($Pt$)$ is widely used as a surface catalyst for various gas reactions due to its good

adsorption properties for gases. Suppose CO is adsorbed on a Pt$(100)$ surface forming a

$Pt(100)-(21)CO$ structure. If $CO$ is adsorbed at the bridge site as shown in the figure, draw

the real lattice $($using o for Pt and $x$ for $CO$ for simplicity$)$ and then draw the resulting LEED

pattern. Also, indicate the unit vectors of the real lattice and the reciprocal lattice.