Highwood Park is constructing a children's play area that will be completely fenced
with three entrance and exit gates. The number of feet of fencing needed to enclose
the children's play area can be determined using the formula f = 47(a + 9) – 16
where f represents the feet of fencing and a represents the area. If Highwood Park
has 420 feet of fencing, what is the area of the space?