1/4" = 1'
convert 3 1/2 into an improper fraction with a denominator of 4:
3 1/2" = 7/2" = 14/4"
1/4" = 1', so 14/4" = 14'
this side measures 14ft.
next, convert 5 1/4" into an improper fraction:
5 1/4" = 21/4"
1/4" = 1', so 21/4" = 21'
this side measures 21 ft.
The answer is C. 14 ft by 21 ft