b (?) and c
m and n have the same slope (-2/5) so m//n
441ft² (i believe this is the answer, idk though, i might be wrong sorry)
first off let's convert the mixed fractions to improper fractions.

she already did half a hat, so we can say 
so she only needs enough fabric to make 3 more full hats, we know each one uses 9/7 ft, so

I believe the range is 25.