a) length of the fence=back+side+side
=14+8.75+8.75
=31.5m
b) one post is need at the end of one side,one is need at the left corner,one is need at the right corner,one is need at the end of the other side,so there are 4 fence posts are needed.
c) total cost=4*$13.99+3*$4.75
=$238.09