If 2s = a + b + c, then the value of s(s - c) + (s - a) (s - b) is?

Answer: Option A

$$\begin{array}{rl}& \text{According to the question,}\\ & \text{If ,}2s=a+b+c\\ & \iff s=\frac{a+b+c}{2}\\ & \text{Let, }\\ & a=10\\ & b=10\\ & c=10\\ & \because s=\frac{a+b+c}{2}\\ & \Rightarrow s=\frac{10+10+10}{2}\\ & \Rightarrow s=\frac{30}{2}\\ & \Rightarrow s=15\\ & \therefore s\left(s-c\right)+\left(s-a\right)\left(s-b\right)\\ & =15\left(15-10\right)+\left(15-10\right)\left(15-10\right)\\ & =75+25\\ & =100\\ & \text{Now check from option, }\\ & \text{Option ’A’ }ab=10\times 10\\ & =100\left(\text{Satisfied}\right)\end{array}$$