Lucy has been asked to construct as many unique triangles as she can that have all sides of integer length, one side of length 7 cm, and a perimeter less than or equal to 20 cm. Find the number of unique triangles, isosceles triangles, and triangles with perimeter exactly equal to 20 cm that Lucy can construct. A.
23 unique triangles, 8 isosceles triangles, and 2 triangles with perimeter equal to 20 cm
B.
21 unique triangles, 9 isosceles triangles, and 3 triangles with perimeter equal to 20 cm
C.
19 unique triangles, 7 isosceles triangles, and 4 triangles with perimeter equal to 20 cm
D.
22 unique triangles, 10 isosceles triangles, and 3 triangles with perimeter equal to 20 cm