请教NN

1. A square piece of sailcloth is trimmed by 4 feed on one edge to form a rectangular piece, which is then cut in half to create two triangular sails. If the area of each of the sails is 240 square feet, what was the perimeter of the original piece of sailcloth?

a. 75

b. 88

c.96

d.104

e 576

我的式子为: 240*2=480/4=120, 120*4=480

2. If the total cost of a housing project with f units is $1750,000 if half as many units were bukt for the same same total price, the cost per unit would be &250,000, what was the cost per unit for the housing project?

I just wonder how can get the answer based on the these conditions?

1. 式子为 (x-4)*x=240*2=480 =〉x=24=> perimeter=24*4=96

2. 方程：unit cost*units=1750000

250000*units/2=175000

calculate units, then calculate unit cost