Question : Simplify:
$(2 a-3 b-c)^2-(a+2 b+c)^2$

Option 1: $3 a^2+5 b^2-16 a b+2 b c-8 a c$

Option 2: $3 a^2+5 b^2-8 a b+2 b c-6 a c$

Option 3: $3 a^2+5 b^2-16 a b-6 a c$

Option 4: $3 a^2+5 b^2-16 a b+2 b c-6 a c$

Question : a : b = 5 : 8 and b : c = 2 : 6. If a = 25, then find the value of c.

Option 1: 90

Option 2: 140

Option 3: 120

Option 4: 96

Question : If $a+b+c=5, a^3+b^3+c^3=85$, and $abc=25$, then find the value of $a^2+b^2+c^2-a b- bc - ca$.

Option 1: 2

Option 2: 4

Option 3: 6

Option 4: 8

Question : If a : b = 4 : 5 and b : c = 3 : 10, then a : c is:

Option 1: 4 : 10

Option 2: 5 : 3

Option 3: 25 : 6

Option 4: 6 : 25