#### Answer

a)
5 ft x 1 ft = 5ft$^{2}$
4 ft x 2 ft = 8ft$^{2}$
3 ft x 3 ft = 9 ft$^{2}$
b)
3 ft x 3 ft has the greatest area.

#### Work Step by Step

Area of a rectangle: $A$ = $l$$w$
Area of a square: $A$ = $s$$^{2}$
$A$ = $l$$w$
$A$ = (5 ft)(1 ft)
$A$ = 5ft$^{2}$
$A$ = $l$$w$
$A$ = (4 ft)(2 ft)
$A$ = 8ft$^{2}$
$A$ = $s$$^{2}$
$A$ = (3 ft)$^{2}$
$A$ = 9 ft$^{2}$